The Conservatives claim to have exposed widespread evidence of gaming to meet the four-hour A&E waiting time target.

Patients were regularly being moved to emergency assessment or clinical decision units so hospitals did not breach the four-hour A&E target, the Tories said, with patients then left in these units for days on end.

They collected figures under the Freedom of Information Act (FOI) relating to 111 NHS trusts across England. The Tories say the figures suggest patients wait an average of 17 hours on assessment units before receiving a diagnosis and being moved to an appropriate ward.

Overall, there were 32 emergency units, 20 clinical decision units and nine admission units in the FOI sample. Some patients were on the units for 32 days, which the Tories said are usually mixed-sex and often do not contain proper beds, only trolleys.

Shadow health secretary Andrew Lansley said: “Labour complacently claim that they have abolished long waits for patients being admitted to hospitals, but these figures show that all they have really done is fiddle the figures. It is unacceptable and has to change.”

But health minister Gillian Merron said: “Waiting times across the NHS are now shorter than ever before.

“The figures presented by the Tories today are misleading and have been deliberately combined with those of assessment units - where patients who need further observation or investigation before a diagnosis can be made are treated.”

This is not the first time concerns have been raised about trusts using strategies to get round the target.

John Heyworth, president of the College of Emergency Medicine, told BBC Radio 4’s Today programme: “There is no doubt that the four-hour target continues to cause significant pressure on emergency departments across the country on a daily basis, and managers are under severe pressure to comply.

“Inevitably, therefore, they are tempted to use strategies which may allow the clock to stop ticking which may not always be in the patient’s best interest.”

NHS Confederation policy director Nigel Edwards said it was likely patients were being moved because the “clock is ticking”. This was often to provide more time for tests, he said.

He added that there was “not very much leeway” with the four-hour target. “It does on occasions lead to people being moved,” he said.