Jeremy Hunt has refused to deny claims that he rejected a deal on junior doctors contracts that could have averted Wednesday's industrial action.
Junior doctors across England are due to go on strike from 8am as part of a continuing dispute between the Government and the British Medical Association (BMA).
The Health Secretary on Tuesday urged the BMA to "put the interests of patients first and reconsider their refusal to negotiate" on the one remaining issue of weekend working.
He also suggested the new contract will be imposed if an agreement cannot be reached.
But Mr Hunt side-stepped a question from shadow health minister Justin Madders when he asked if the Health Secretary had blocked a "cost neutral proposal" put forward by the BMA.
Mr Madders said: "Today's Independent reports that a potential deal on the junior doctor contract was put to the Government which would have resolved junior doctors' concerns without costing any more money and potentially avoided tomorrow's industrial action.
"A source close to the negotiations said this to the newspaper and I quote: 'The one person who would not agree was the Health Secretary. Even though the NHS Employers and Department of Health teams thought this was a solution, he said no'.
"So 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?"
But Mr Hunt refused to answer the question directly as he attacked Labour for failing to condemn the industrial action.
He said: "The only reason that 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 is the only outstanding issue. If they are prepared to negotiate and be flexible on that so are we.
"What is noticeable is despite 3,000 cancelled operations no-one in the Labour Party is condemning these strikes."
Ministers have repeatedly said that they reserve the right to impose the new contract should a deal fail to be reached.
But Mr Hunt today went even further by linking the contract issue with the Government's intention of creating a seven-day NHS.
He said: "The party opposite are saying that if a negotiated settlement can't be reached we should not impose a contract.
"In other words we should give up on seven-day care for the most vulnerable patients.
"There was a time when the Labour Party used to speak up for vulnerable patients but now it is clear that unions matter more than patients."