Britain's top stroke doctors have accused Jeremy Hunt of "misrepresenting statistics" to justify his seven-day NHS.
Professors and prize-winners are among 59 who blasted the Health Secretary's statement that stroke patients are 20% more likely to die on weekends.
And they warned claims like his have already harmed stroke patients because they are putting people off seeking help on the weekend.
Labour's shadow health secretary Heidi Alexander told the Mirror: "This isn't the first time Jeremy Hunt's statements have been questioned by experts.
"His careless use of statistics is one of the main reasons why junior doctors feel so angry.
"Patients and junior doctors want to see a resolution to this dispute, not more deeply questionable comments from Ministers, which just fan the flames of disagreement."
The attack is the latest in a long line on Mr Hunt's use of statistics and comes amid reports he could be sacked and replaced with Boris Johnson.
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One cabinet minister told the Sunday Times Mr Hunt "was sent to health to keep the NHS out of the headlines - and instead we’ve got the first doctors’ strike in a generation".
Mr Hunt made his bold statement on Tuesday as thousands of junior doctors staged a historic 24-hour walkout over pay and hours.
But today his claims were trashed by medics including Martin Brown, Professor of Stroke Medicine at UCL and a former President of the British Association of Stroke Physicians.
Their letter, published by the Sunday Times , said the Tory minister had used out-of-date data from before "rapid improvements in stroke care".
Improvements in the NHS included new acute stroke units which have reduced death rates by a quarter, the doctors said.
They wrote: "Recent audits of stroke outcomes in London show that there is no longer any excess of hospital deaths in patients with stroke admitted at the weekend."
The doctors added there was "always room for improvement" but wrote: "This is not about a lack of junior doctors at weekends but the healthcare system as a whole, and the problems won’t be solved by spreading existing resources ever thinner across the week.
"Misrepresentation of statistics on stroke care to justify the junior doctor contract proposals is inappropriate.
"Previous statements about the quality of weekend services at hospitals, highly publicised in the press, led patients to defer seeking medical help and come to harm.
"Timely presentation to hospital is particularly critical in stroke, as it improves outcomes and reduces mortality, and the minister needs to reassure the public about the level of weekend stroke services."
It comes after Professor David Curtis of UCL, who has written more than 100 reports on medical statistics, told the Mirror the Health Secretary was "lying" because he left key context out of his argument.
The psychiatrist and honorary professor at University College London said far more people were admitted for strokes on weekdays than weekend days - 111 per 100,000 compared to just 88.
That meant it was likely only the most serious cases - so the ones more likely to die - went to hospital on the weekend.
And even though the stroke death rate was higher at weekends for people in hospital - 12.9 per cent compared to 11.1 per cent - it was lower as a percentage of the population.
Mr Hunt denied Prof Curtis' attack, saying his comments were "not hardball, just facts" and the report on strokes he quoted was just one of eight showing higher weekend death rates.
He said many factors caused weekend deaths, pointing to a study that adjusted for severe cases being admitted after-hours and still showed death rates 11% higher.
He added: "Isn't it the duty of the Health Secretary to act?"
A Department of Health spokesman added today: "Anyone with urgent health concerns should seek advice as soon as possible.
"However, there is clear clinical evidence that standards of care are not uniform across the week - the Freemantle study in the BMJ and clinical evidence from NHS England show that stroke patients have a 20 per cent greater risk of dying if admitted at the weekend.
"This Government makes no apology for tackling the problem.”