Amy Winehouse has been offered the staggering sum to perform at the Costume Institute Gala Benefit at New York's Metropolitan Museum of Art on May 5, organised by institute co-chairs George and Julia.

"Amy was taken aback when she learned that George Clooney and Julia Roberts were after her.

"Their representatives have been phoning her offices and sending dozens of emails to convince her to take part. She's seriously considering their generous offer.

"She hasn't really taken it in - and keeps saying that her life is getting more surreal by the second." The glitzy bash is being hosted by fashion designer and honorary chair Giorgio Armani, who is a huge fan of the Grammy Award winner and pleaded with organisers to ask her to be involved." - a source said.                                                                           

Winehouse's potential £500,000 pay packet is dwarfed by what some other musicians charge for private performances. The Rolling Stones demand up to £4 million - making them the most expensive party act on the planet.

The Eagles charge £3.75 million, while Canadian singer Celine Dion can command up to around £3.3 million.