Theresa May has again been accused of using deliberately misleading statistics to play down the severity of the winter crisis in the NHS.

Welsh First Minister Carwyn Jones has written to the UK Statistics Authority (UKSA) about the Prime Minister’s “selective misuse” of data following her attempt to deflect criticism of the health service’s performance onto the Welsh NHS at Prime Minister’s Questions.

Mr Jones' intervention is the second time the Government has been called up on its use of statistics, with senior Tory MPs condemning the “disingenuous” use of data to stifle the much needed discussion about NHS pressures.

In the Commons on Wednesday Ms May claimed the number of patients forced to wait more than 12 hours in A&E in Wales, which has a Labour government, is nearly eight times higher than in England.

However hospitals in England only measure 12 hour waits from the time a senior clinician has seen the patient and made a decision that they should be admitted.

In Wales the countdown begins at the point the patient registers at A&E.

Senior NHS doctors told The Independent the English figures “in no way reflect the time patients spent in A&E” and warned that actual numbers of breaches may be higher.

Ms May, at Prime Minister’s Questions, said: “The latest figures show that, in England, 497 people were waiting more than 12 hours, but the latest figures also show that, under the Labour Government in Wales, 3,741 people were waiting more than 12 hours.”

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His warning followed a winter crisis that saw staffing and funding shortages leading to tens of thousands of operations cancelled and doctors warning patients were “dying prematurely” in corridors.

In his letter to Sir David Norgrove, chairman of the UKSA, Mr Jones said comparable figures reveal England performs far worse.

NHS Digital data on 12 hour waits in 2016-17 shows there were 262,367 patients waiting more than 12 hours in A&E, compared to 3,502 who waited more than 12 hours for admission after a decision to admit.

Mr Jones said the figures were “simply not a valid comparison of accident and emergency performance” and called for an investigation.

“The selective misuse of statistics like this does not allow for a fair debate on the NHS,” he added.

When asked about the figures by The Independent the Department of Health and Social Care claimed Wales still performed worse with comparable data, although it shows this by a much smaller margin, but the Department was unable to provide the figures it had used to establish this.

Conservative MP, and chair of the Commons Health Committee, Dr Sarah Wollaston, has already criticised the Government’s misuse of winter data, after she had tried to ask about the lack of beds in hospitals.

Health minister Philip Dunne claimed bed occupancy was below safe levels, but cited the only day this winter where that was true: Christmas Eve.

Mr Dunne lost his position shortly afterwards in the Cabinet reshuffle.

A spokesperson for the Royal College of Emergency Medicine told The Independent: "It is wrong to compare 12 hour breaches in England and Wales.

“The 12 hour wait statistics for England in no way reflect the actual time the patient is kept waiting and we suspect that the number of breaches is actually much higher than is being reported.

“The College has long argued for this metric to be changed to start at the moment the patient arrives.”

A Department of Health and Social Care Spokesperson said: “The latest annual data shows the number of patients spending more than 12 hours in A&E in Wales is proportionately 2.6 times higher than in England.