Kelly Osbourne is in rehab because of London's "party atmosphere".
Friends of the 24-year-old star have blamed Kelly's wild lifestyle in the UK city for her latest stint in rehab.
A source said: "It's a very party atmosphere there.
"Kelly just tends to get back into that rut when she's there since her friends are there, and she's just more comfortable there. The old party habits come back."
It has recently been reported Kelly's dad - rocker Ozzy Osbourne - has sent his troubled daughter to the same tough boot-camp-style rehab clinic which helped him kick his addictions to alcohol and drugs.
Kelly is rumoured to have checked into the Hazelden Alcohol and Drug Rehabilitation Center in Oregon, US, last week.
Kelly's mother Sharon Osbourne confirmed she was seeking treatment but has not revealed further details about her stay.
She said at the time: "Yeah, Kelly's in rehab. What else can we say? She knew that it was the right thing to do at this point and we're proud that she did it. The family is all standing behind her. Kelly knew that she needed help and she's getting it."
Sharon emotionally added: "Kelly will tell you herself when she gets out. We just pray that everything's going to be OK.
Kelly - who is expected to stay at the rehab centre for 30 days - was arrested for common assault on January 2, and has been bailed until a date in March.