Britney Spears parties with Paris Hilton, leaves underwear at home

They have already been dubbed "The Brit Pack": three girls, increasingly famous for making spectacularly bad choices, marshaling their collective brain power to navigate the booths and banquettes at Hyde or Spider Club or wherever it is they're drinking it off on any given night.

Paris Hilton, her frenemy Lindsay Lohan and newly separated Britney Spears: three party girls without a care (babies? what babies?), a high tolerance for alcohol or a good publicist.

In the past week, Spears who has a 1-year-old and 2-month-old at home has spent every single night partying with Hilton (and, occasionally, Lohan).

A quick study, Spears long absent from the scene, what with being married and pregnant and all has already picked up such "It" girl tricks as how to make sure your picture winds up everywhere.

Such as, don't wear underwear and flash your crotch while pretending you hate the paparazzi and tearfully begging for them to leave you alone.

After dumping Kevin Federline, Spears seemed like she was on the upswing: She cut her hair. She looked like she was bathing regularly. She celebrated her separation with some wholesome ice-skating at Rockefeller Center and even more wholesome shopping for chunky sweaters and beanie caps! at the Gap. She started recording her comeback album, working late nights at the Sony studios in Manhattan.

Then she took off for a Vegas weekend, where she reconnected with old friend Hilton, and then Lindsay Lohan started angling to get in on this power clique, which she eventually did, and now all is well and the trio go clubbing every night, smoking and drinking and having dance-offs.

Meanwhile, Spears and Hilton have been tapped to co-host the Billboard Music Awards at the MGM Grand on Monday, the New York Post's Page Six column reported.