David Cameron has turned to Simon Cowell to bring a populist touch to the Conservatives’ presentation in the build-up to the next election.

The impresario helped to recruit the finalists of ITV’s talent show Britain’s Got Talent for a children’s party hosted by Mr Cameron at a London hospital on Monday. The acts, currently on tour, performed free at the Evelina Children’s Hospital during the event. Two of the finalists of the show, on which Mr Cowell was a judge, later appeared at a Conservative fund-raising ball hosted by Mr Cameron and his wife, Samantha.

Mr Cameron announced his intention to hold a party to mark the 60th anniversary of the National Health Service in the new year. Insiders say that he cooled on the original format of a tea party for health service workers as the anniversary approached, however.

The idea of a children’s party featuring the stars of the popular talent show emerged from a dinner that Mr Cameron had with Mr Cowell last month. The music mogul is a friend of Andy Coulson, Mr Cameron’s press secretary. Senior Tories say the event was scheduled to coincide with the publication of the NHS Next Steps Review.

Nick Clegg, the Liberal Democrat leader, said: “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. They also say that An-drew Lansley, the Shadow Health Secretary, prefigured Monday’s review by Lord Darzi of Denham with a detailed set of alternative policy proposals.

A spokesman said that the Cameron-Cowell dinner had been a private function. A party source said that Signature, a bhangra dancing duo who later performed at the Tories’ summer ball, were Conservative supporters. The act was joined by another finalist, the 12-year-old opera singer Faryl Smith, who had not originally been booked but asked to appear.

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