However, speaking to the BBC, the Tories pointed out some of the 140 doctors who had signed the letter were public Labour supporters and advisers.
Published in The Guardian, the letter claimed the last five years had been characterised by “broken promises, reductions in necessary funding, and destructive legislation”, suggesting that "if things carry on as they are then in future people will be denied care they once had under the NHS and have to pay more for health services".
It also criticised funding reductions for local authorities, a failure to meet A&E waiting time targets, and widespread problems with mental health services.
But a spokeswoman for the Conservative Party said the claims were wrong.
The facts are clear: we have cut the number of managers and increased funding for the NHS so we can have 9,500 more doctors and 6,900 nurses treating patients.