The young star of TV's Britain's Got Talent sang at a Conservative fund-raising ball hosted by Tory leader David Cameron and his wife, Samantha.

Earlier, the 12-year-old, along with all the finalists from the ITV show, had performed at a children's party hosted by Mr Cameron at a London hospital.

Mr Cameron announced his intention to hold a party to mark the 60th anniversary of the National Health Service.

According to reports, he cooled on the original format of a tea party for health service workers as the anniversary approached, however, and the idea of a children's party featuring the stars of the popular talent show emerged from a dinner that Mr Cameron had with Simon Cowell, the man behind Britain's Got Talent.

Hear young Faryl sing Amazing Grace - click here

Nick Clegg, the Liberal Democrat leader, said in The Times: "This bizarre attempt to latch on to the popularity of light entertainment only serves to highlight the fact that beneath his showbiz veneer, David Cameron has nothing of substance to say about the NHS.

"With the NHS in desperate need of reform, and the Government merely tinkering, you would expect the Tory leader to have something serious to say.

"But when faced with serious issues, David Cameron has once again resorted to gimmicks."

Laura Moffatt, parliamentary aide to Alan Johnson, the Health Secretary, said that the event showed that Mr Cameron had nothing to say.

"His health policy is a content-free zone – filled with birthday cakes and dancing," she said.

Senior Tory figures insisted, however, that the event was a legitimate attempt to reassure voters that the party cared about the NHS on a day when public attention was focused on the health service.

Signature, a dancing duo, also performed at the Tory event.