George Michael arrives at Brent Magistrates Court in London, May 8, 2007. [Reuters]

Singer George Michael said he felt "very ashamed" as he pleaded guilty on Tuesday to driving while unfit due to drugs after police found him slumped at the wheel of his car in London.

The 43-year-old blamed his behavior on a mixture of tiredness and prescription medicine.

"I did something very stupid," he told a court without giving details of any drugs he had taken, media reports said. "I am perfectly aware that I did something very wrong and got into my car when I was unfit to drive.

"I was not in my normal physical state and I am perfectly prepared to accept the correct punishment for that and I would have accepted it a long time ago."

He has yet to be sentenced and faces a further hearing on May 30 for the court to consider his guilty plea, a Crown Prosecution Service spokeswoman said.

The charge carries a maximum six-month jail term and a fine of up to 5,000 pounds ($9,968).

Michael, who arrived at Brent Magistrates Court in London looking relaxed in a black jacket, black shirt and jeans, is due to start a European tour later this month.

The singer has had a series of brushes with the law.

In April 1998 he was arrested for engaging in a "lewd act" in a public toilet in Los Angeles, after which he ended years of speculation over his sexuality by announcing that he was gay.

He angered mental health charities last year by smoking a cannabis joint during a television interview and saying: "This stuff keeps me sane and happy."