Singer Bruno Mars is still haunted by his 2010 drug bust in Las Vegas, insisting he has to "try every day to forget" the scandal.

The Grenade hitmaker ran into trouble with the law when a bathroom attendant at the Hard Rock Hotel in Sin City called cops to report the star's drug-dabbling.

Mars is said to have told officers it was his first time using drugs when he was allegedly caught with a bag of cocaine, and now admits the arrest still weighs heavy on his conscience.

In a candid interview with America's GQ magazine, he says, "I don't know where that (story about it being my first time) came from. I was really intoxicated. I was really drunk. So a lot of that is a big blur, and I try every day to forget and keep pushing."

When asked why he was grinning in his police mugshot, Mars replied, "I have no idea... It was a picture."

Mars was placed on probation and ordered to complete eight hours of drug counselling as well as 200 hours of community service. The cocaine possession charge was dismissed by a Las Vegas judge last year (Jan12).