Robbie Williams has been admitted to rehab for addiction to prescription drugs on his 33rd birthday.The 'Rudebox' singer checked into a US facility, but it is not yet known where the centre is or what drugs he has become dependent on. His spokesperson Bryony Watts said: "Robbie Williams has today been admitted into a treatment centre in America for his dependency on prescription drugs.There will be no further comment on this matter."The announcement comes just months after Robbie cancelled his Asian tour in September citing stress and exhaustion. Robbie previously checked into rehab to be treated for drug use and alcoholism shortly after he quit Take That in 1995. Afterwards, the singer admitted his substance abuse was so bad his friend Sir Elton John had to"kidnap" him, take him to his home and force him into rehab. Robbie's decision comes on the eve of the BRIT Awards - at which Take That and long-term rival Oasis are set to be honoured. Oasis, fronted by Liam Gallagher who Robbie has been feuding with for years,will receive the Outstanding Contribution To Music award and close the prestigious event with a performance of their greatest hits.Take That are up for the British Single prize, for their number one hit 'Patience', and will round off their incredible comeback - which has included a sell-out UK tour and number one album - by performing on Wednesday night. Despite winning a phenomenal 15 awards, Robbie has only one nomination this year, British Live Act. His omission from the British Male and Master Card British Album categories -the first time this has happened for years - follows disappointing latest sales of his latest album 'Rudebox'. Labels: BRIT AWARDS, DRUGS, REHAB, ROBBIE WILLIAMS, RUDEBOX