The NHS is suffering under the coalition say GPs

The letter warned the NHS was “withering away”, while the growing involvement of commercial companies meant in future people would be denied care they once had under the NHS while having to pay more for health services.

The signatories to the letter include Dr Clare Gerada, a former chair of the Royal College of General Practitioners; Prof John Ashton, retired director of public health; epidemiologist professor Michel Coleman; Simon Capewell, professor of public health in Liverpool; Trisha Greenhalgh, professor of primary care at Oxford; Martin McKee, professor of European public health, and Raymond Tallis, emeritus professor of geriatric medicine in Manchester.

The letter comes just a week after more than 100 leading business figures sent an open letter to The Daily Telegraph backing the Government’s economic strategy.

The Conservatives claimed the doctors’ letter had been orchestrated by Labour in a further attempt to “weaponise” the NHS in the election.

The letter was particularly critical of the reforms driven through by Conservative former health secretary Andrew Lansley in the Health and Social Care Act 2012.

“Privatisation not only threatens co-ordinated services but also jeopardises training of our future health care providers and medical research, particularly that of public health,” it says.

The doctors, who urged people to use their votes in the General Election to ensure “the NHS in England is reinstated”, said the changes were affecting patient services.

“People may be unaware that under the coalition, dozens of accident and emergency departments and maternity units have been closed or earmarked for closure or downgrading,” it said.

“In addition, 51 NHS walk-in centres have been closed or downgraded in this time, and more than 60 ambulance stations have shut.”

A Conservative spokesman said: “Ed Miliband wants to ‘weaponise’ the NHS for his own political gain.”