The Conservatives warned that 92 of England's 204 A&E departments would go if guidance attributed to the Department of Health was imposed nationally.

They said that the guidance called for A&Es to serve a minimum 450,000 population, when the average A&E unit currently serves just under 250,000 people.

But they claimed that the 450,000 figure "is only being used to justify closures in those areas saddled with large deficits - suggesting that the figure has been plucked out of thin air to justify closures which are actually being driven by financial concerns".

But Health Minister Andy Burnham said: "It is complete nonsense to suggest that half of all A&E's are marked for closure. This is outrageous scaremongering by the Tories.

"They know these allegations are not true and it is deeply irresponsible to worry the public in this way."

The Tories cited a document prepared by the West Surrey NHS, which said: "Current Department of Health and Strategic Health Authority guidance suggests that to be viable in terms of patient need, patient safety, staffing numbers and clinical training requirements, a full A&E department in the future would need to be supported by a catchment population of between 450,000 and 500,000 people."

The Conservatives also pointed out that the Department of Health's director of emergency care, George Alberti, recently recommended the closure of an A&E in north London, which would leave the remaining two A&Es serving with catchment populations of 450,000 each.

Shadow health secretary Andrew Lansley said: "There is no clinical evidence which would justify shutting down A&E departments simply because they don't serve a catchment population in excess of 450,000."