POP babe Britney Spears wed her childhood sweetheart in a drunken prank — and 12 hours later wanted the marriage axed.

Wearing torn jeans and a baseball cap, she tied the knot with Jason Alexander in Las Vegas at 5am.

But the Oops I Did It Again star panicked when she later realised what she had done and told her lawyers to get Saturday’s quickie marriage annulled.

A close pal of Britney, 22, said last night: “She had been partying for two days straight and was definitely still in a party mood when they decided to do it.

“But then it turned into, 'Oh my God, what have I done!”

The hung-over star last night admitted her shock marriage was a joke that went too far — telling pals: “It seemed like a funny idea at the time.”

The singer and childhood sweetheart Jason, also 22, were said to be “laughing and giggling” as they wed in a 15-minute quickie wedding early on Saturday.

But when Britney started to sober up the prank no longer seemed so funny.

She rang her lawyers in a panic, ordering them to get the marriage annulled as soon as possible — using any method necessary.

And last night a friend of the singer said: “It was just a drunken lark. Britney and Jason had been partying for two days straight when they decided to do it.

“She said something like, ‘Wouldn’t it be funny if we got married — oh let’s just go and do it!’ But then it turned into ‘Oh my God, what have I done!’ Suddenly it was a joke that just went too far.”

The friend told how Britney gradually became more and more horrified by the prank as the effects of the booze wore off.

The pal added: “She thought it was funny all Saturday morning. But by about 5pm on Saturday she realised what she had done and what a terrible mistake it had been.

“Not least among her worries was what her mother Lynne would say — she didn’t know anything about the wedding. She has brought Britney up to respect the sanctity of marriage — and Britney knew she would be very angry.

“After all, it was not a case of a whirlwind romance leading to true love. It was just a stupid, crazy spur-of-the-moment idea.”

Last night sources close to Britney said she and her advisers had already met with Jason to sign the legal papers that will begin the annulment process.

The documents will be presented to a judge today. If he grants the annulment Jason will not be entitled to any of his former wife’s huge earnings — because legally it will be as if the marriage never took place.

A spokesman for Britney's record company Jive said the star had already applied for an annulment and was expecting it to come through today.

He said: “On January 3, Britney Spears and a friend took a joke too far by getting married. Ms Spears and Mr Alexander have filed for an annulment, which will become official on Monday, January 5.”

The wedding fiasco has added to concerns that Britney is on the edge of a breakdown.

During a recent TV interview she sobbed over ex-boyfriend Justin Timberlake and revealed she was desperate for a new lover.

Yesterday a Hollywood divorce lawyer said: “For Britney to do what she did is suicidal. She is worth $100million plus — so to wed without a pre-nuptial agreement is financial madness.

“Her lawyers must have had heart attacks when they heard. Luckily for her if it is annulled Jason is entitled to nothing.”

Britney and Jason made the snap decision to marry after spending two days knocking back drinks at Las Vegas’s plush Palms Hotel. The singer checked into the £6,000-a-night Real World suite using the name Alotta Warmheart.

One onlooker said: “They were in high spirits — it was definitely a party atmosphere.”

Britney and Jason, who is from her home town of Kentwood, Louisiana, took a limo from the hotel to the Little White Wedding Chapel, where Demi Moore and Bruce Willis tied the knot.

The couple were accompanied by security guards from the hotel, which is owned by her former boyfriend George Maloof.

But Britney, wearing jeans and a baseball cap, and Jason were told by chapel staff they needed a licence before they could marry.

So they bundled back into the limo and drove to the nearby Las Vegas Marriage Bureau which is open 24 hours.

They queued up with other couples to pay the £30 licence fee and fill in forms giving names, ages and addresses.

Deputy Marriage Commissioner Joyce Singer revealed: “Britney was accompanied by a very nice gentleman. My colleague served them at the counter. It was over very quickly. They were probably in there about half an hour.”

Mrs Singer insisted Britney showed no signs of being drunk. She added: “She was sober. We are not allowed by law to give a licence to anyone who is under the influence.

“But Britney and Jason were both fine and therefore we gave them the licence.”

Lynda Wells, who served Britney and Jason, claimed they seemed “deadly serious” about marrying.

After getting the licence the couple were driven back to the chapel. There, they opted for the budget-price service — which took about another 15 minutes.

Britney was escorted down the aisle by a barman from the Palms hotel. The ceremony was witnessed by just a handful of people, including chapel staff. A cameraman videotaped it for Britney, charging her £75.

The chapel owners gave Britney and Jason a heart-shaped card containing the recipe for a successful marriage.

It read: “Take two hearts full of love, two cups of friendship and four armfuls of gentleness.”

The couple were then taken back to Palms where they celebrated in Britney’s suite with more drinks and champagne — and giggled while they watched the video. Britney and Jason had gone to the hotel to celebrate the New Year — and immediately began hitting the booze.

Las Vegas columnist Norm Clarke said she was spotted behaving outrageously. He added: “Britney was in a VIP booth and had the crowd buzzing about her behaviour.

“She was spotted kissing one of her female dancers — smooches that made her infamous recent kiss with Madonna at the MTV Awards look tame.”

Hotel insiders said Britney had to be carried out of its nightclub on the first night after drinking too much.

Mr Maloof admitted Britney had needed help leaving the club but claimed it was because she was tired after a long flight.

She was back the next night partying again with Jason — before apparently deciding on the spur of the moment to get hitched. Some cynical sources claimed the marriage was a stunt to promote Britney’s new album In The Zone.

She has embarked on a series of outrageous stunts in recent months including the famous Madonna snog at the MTV music awards in New York. But a Britney insider said: “Getting married just to sell records is a bit drastic — even for her.”

Under Las Vegas law the marriage could be scrapped within two weeks.

There are numerous grounds on which Britney could apply for annulment, including “intoxication, or substance abuse, causing lack of consent by either party”.

She could also claim the marriage was never consummated or that either party “misrepresented” their willingness to live together as man or wife after the marriage.

Or because either party had acted on “mistake, accident or impulse”. Britney could also claim it was not valid because “one person misrepresented that she/he was in love with the other party prior to the marriage”.

She might also claim one of them went through with the marriage “to secure access to the other party’s money or property”.

If the annulment has been agreed by both parties a joint application will go before a county court judge. He will decide whether scrapping the marriage is justified.

If Jason were to contest the annulment, Britney could have a harder fight.

She would have to provide substantial evidence that her reasons for wanting the marriage annulled were valid. If she couldn’t she would be forced to consider divorcing Jason which might end up costing her millions.

WITH her ravaged skin, oversize sunglasses, scruffy clothes and ever-present cigarette the girl above looks like classic US trailer trash.

But this isn't the latest guest on the Jerry Springer Show - it is music's latest car crash, the once-perfect pop princess Britney Spears.

Formerly a squeaky-clean image of innocence, Britney is engulfed in a downward spiral which is stealing her looks and her dignity.

And those close to her fear the 22-year-old's freefall is frighteningly similar to that of original wild child Courtney Love, widow of Nirvana singer Kurt Cobain.

Since Britney injured her knee in a fall on a video shoot last month she has really let herself go.

Emerging for only a few hours a day in grubby clothes and puffing on a cigarette, she has become a freak show for photographers.

And critics can only speculate what she is doing all day behind the closed doors of her New York and Beverly Hills homes.

The new fixture in her life is fiancé Kevin Federline, who her aides describe as "bad news."

He has some serious baggage - a pregnant ex-girlfriend, Shar Jackson, the mother of his two-year-old daughter Kori.

But Britney was smitten. Before long she was threatening to cancel gigs just to be with him and the pair became inseparable as she completed her European tour.

When knee surgery forced Britney to cancel her world tour, it seemed to suit her.

She jumped on a plane, got engaged above the Atlantic and has since had an excuse to lounge about all day with her new fella.

She now looks bloated, spotty and dishevelled.

The marriage is scheduled for November - the second time she will have been hitched this year after her fateful 55-hour union to Jason Alexander.

If Britney gets anywhere near Courtney's excesses it will be a big worry. At 38, the former Hole singer is in a bad place.

Drugs and drink have wrecked her appearance and over the past 15 years she has been as famous for her outrageous appearance and behaviour as for her acting or music.

Of course, Britney is a long way from the depths of depravity Courtney has descended to.

Indeed, the young singer swears she has never done drugs and called in her lawyers in a fury last year after claims she had been seen snorting cocaine in a nightspot.

But those close to her are still worried. One former aide said: "This is a very different Britney than we ever saw before.

"She let her hair down when she split from Justin Timberlake but she really looks trashy now.

"This is the start of a very slippery slope. Once she starts piling on the weight she'll find it difficult to get back her old figure.

"Her skin and hair look a mess. I wonder what is really going on with her. Her skin has always been bad but she doesn't seem to be doing anything about it. And the amount she is smoking and drinking can't help.

"This new guy Kevin seems happy just to let her lose her looks completely. Personally, I think he is bad news and, let's face it, he doesn't come with a good track record.

"He has left a pregnant woman and a child to hook up with Britney and now they are getting married after a couple of months. It's all going out of control for Britney."

Ironically, the one thing this turbulent time in Britney's life DOESN'T seem to have affected is her record sales.

Her last two singles, Toxic and Everytime, have been UK No1s.

In her current condition they could turn out to be her last, albeit successful, UK singles.

And if that is the case even her fiercest critics won't be able to deny she has gone out on a real high.