Jeremy Hunt has been accused of personally vetoing a deal that could have stopped the junior doctor strike.
Thousands of medics will leave their posts for 24 hours from 8am tomorrow - their second walkout in a month - after talks over Saturday pay broke down.
Now the Health Secretary is facing claims he ruled out a deal - despite it being backed by his own negotiators.
A source in the British Medical Association, leading doctors in crunch talks, claimed it dealt with the final sticking point of weekend pay and cost the government no extra money.
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The source told the Independent: "The one person who would not agree was Jeremy Hunt. Even though the NHS Employers and Department of Health teams thought this was a solution he said no."
Mr Hunt's department said the claims were "completely untrue" - but the top Tory refused to categorically deny them in Parliament.
Shadow Health Minister Justin Madders told him: "Let me ask the Health Secretary a very direct question.
"Has the government at any point rejected a cost-neutral proposal from the BMA on the junior doctor contract?
"Yes or no?"
The Health Secretary shook his head - but would not give a one-word answer.
Instead he told MPs: "The only reason we do not have a solution on the junior doctors is because in December on the one outstanding issue, which is about pay on Saturdays, the BMA said they would negotiate, but last month they said they refused to negotiate.
"That's the only outstanding issue. If they're prepared to negotiate and be flexible on that, so are we."
Mr Hunt also tore into Labour after Jeremy Corbyn backed last month's strike and once again raised the "nuclear option" of imposing the contract against doctors' will.
He said: "The party opposite are saying that if a negotiated settlement can't be reached, we should not impose a new contract - in other words we should give up on seven day care for vulnerable patients.
"There was a time when the Labour Party used to speak up for vulnerable patients but now it's clear that unions matter more."
The fresh strike, which follows a 24-hour walkout on January 12, was downgraded from what would have been a 48-hour walkout involving all junior doctors.
Now it will exclude emergency staff, including on A&E, and last for just 24 hours.
Around 160 pickets will spring up across the UK, with BMA reps holding another 20 'meet the doctor' events in major cities including Derby, Manchester and London.
NHS chiefs say 2,884 operations have already been cancelled for the day of the strike.
It is thought the alleged deal could have been offered by the BMA some time before the new year.
NHS Employers chief executive Danny Mortimer said the BMA had offered no "substantive proposals" since 2016 began.
Asked to respond to the claims from the BMA source, a Department of Health spokesman said: "This is completely untrue.
"The BMA has continuously refused to discuss unsocial hours pay, despite their agreement to talk about this as part of ACAS in November and the progress we've made on safety, education and training."
The BMA declined to comment.