David Cameron has upped the ante in the Government's row with junior doctors - claiming 5,000 more deaths occur on the NHS at weekends than previously claimed.
Health Secretary Jeremy Hunt prompted outrage among the medical profession when he first argued in July there were about 6,000 deaths a year because of the lack of "a proper seven-day service".
However, the Prime Minister today doubled down on the claim, contending his Cabinet minister was "guilty of an understatement" and the real total was 11,000.
The "weekend effect" on the NHS has been hotly-disputed.
Ministers have used the notion to justify its push for a new contract with junior doctors which would change their rotas.
The figure stems from a British Medical Journal study from last year - but even its author said it would be “rash and misleading” to suggest people were more likely to die at the weekend because of poorer care.
The excess deaths figure relates to admissions on Friday through to Monday, rather than deaths occurring at the weekend.
Cameron’s comments came during a fiery Prime Minister’s Questions, and followed a BBC story that questioned whether Hunt used unverified and unpublished research to blame junior doctors for weekend deaths.
With junior doctors set for a fresh round of strikes next month, Jeremy Corbyn attacked Hunt's use of the mortality statistics.
The Labour leader accused Hunt of using “misrepresented research”, asking: “Is the PM and his Health Secretary being rash and misleading with these figures?”
Cameron at first offered a decoy, admitting that the dispute “has been plagued by scaremongering and inaccurate statistics”, before claiming it was the British Medical Association, which represents junior doctors, that had made “completely untrue” claims over cuts to pay.
He went on the 6,000 figure for excess deaths was based on a question asked by the Health Secretary to Sir Bruce Keogh, the medical director of the NHS, and continued: “The Health Secretary was indeed guilty. He was guilty of an understatement.
“The true figures for excess deaths at the weekend are 11,000 not 6,000, so perhaps he will now withdraw his totally unjustified attack on the Health Secretary - will he withdraw it now he knows the figures?"
Corbyn went on that the PM and Hunt should “apologise for what they’ve done”, but Cameron opted to mock the leader of the Opposition instead.
He said: "I think the best thing he said there is he wrote that question before he heard my answer. I note that there's absolutely no withdrawal of his accusation against the Health Secretary even after he gets those figures.”
The data checking website Full Fact immediately tweeted an article pointing out there was “no evidence” to support the 11,000 deaths link.