Britney Spears has been advised to end her friendship with Paris Hilton if she ever wants to rebuild her music career.The 'Toxic' singer - who befriended the hotel heiress after filing for divorce from Kevin Federline last month - has not been seen partying withParis for almost two weeks now. A source told the New York Post newspaper: "Britney has been told by her people that if she ever wants a comeback, she has to stay far away from Paris and start acting like an adult."Britney - who has two sons, 15-month-old Sean Preston and three-month-old Jayden James, with Kevin - was seen enjoying a string of late nights with Paris immediately after dumping Kevin.She was also photographed on four occasions not wearing any underwear.The 25-year-old singer has since apologised to her fans, via her official website, for her behaviour, saying: "Thank God for the new underwear line from Victoria's Secret!"I look forward to a new year, new music and a new me. I'm just getting started!"Britney has not released any music for two years but has been in the recording studios since she filed for divorce.

Paris Hilton and Britney Spears