Amy Winehouse might have to pull out of Glastonbury and the Nelson Mandela concert next week, the singer's spokesman has admitted.

The troubled singer is booked to play at Mr Mandela's 90th birthday concert in Hyde Park on Friday June 27 followed by Glastonbury, directly before headliner Jay-Z, the following day.

But Winehouse, who has fought heroin and crack addiction, is still in a London clinic awaiting the results of tests following her collapse at home.

A spokesman said Winehouse still intended to perform at both high-profile events, but that doctors would decide whether she was well enough to take to the stage.

He said: "Amy has undergone more scans and tests and we are awaiting the verdict of her doctors.

"At present, she still intends to perform at the two scheduled dates next week.

"However, a decision will be made entirely upon the advice of her doctors and in her best interests."

Winehouse, 24, has been in the London Clinic since being taken there by her father Mitch after fainting at her home in Camden, north London, on Monday.

© Independent Television News Limited 2009. All rights reserved.