Jeremy Hunt has been accused of "backtracking" on threats to use powers to impose a new contract on junior doctors.
The Health Secretary is alleged to have altered his position on how a new contract will be brought into force after months of bitter dispute that has led to unprecedented industrial action.
Mr Hunt is said to have climbed down from his initial "nuclear option" stance that weekend working hours will be "imposed" upon junior doctors.
Labour has called on the Health Secretary to clarify his position urgently amid reports the contract will now be "introduced" by other means, as he may not have the legal powers to force the changes.
However the Department of Health (DH) rejected the suggestion there had been a U-turn and said the Government's position remained consistent.
The news comes as lawyers acting on behalf of some junior doctors issued proceedings against the Health Secretary.
Campaign group Justice for Health are arguing that Mr Hunt "has no legal power to impose the junior doctors' contract on the majority of doctors".
Junior doctors are expected to stage a fifth strike on April 26 and 27 when they will fully withdraw labour between the hours of 8am and 5pm.
It will be the first time in this country that doctors have staged a full walk-out. In previous strikes junior doctors provided emergency care cover.
The Health Secretary said the Government had "done what entitled to" after talks with the British Medical Association (BMA) failed.
The body's chairman, Dr Mark Porter, said it was time for Mr Hunt to return to the negotiating table.
"This is just yet more evidence of a Secretary of State blundering his way through the handling of the junior doctor dispute," he said.
"Having announced to Parliament that the Government would impose a contract on junior doctors, he is now backtracking on this.
"His announcement of imposition is directly responsible for tens of thousands of junior doctors taking industrial action, souring relations with the medical profession at a time when the NHS is buckling.
"As things stand, junior doctors will still be faced, come August, with a contract which they have no confidence in and the introduction of which they continue to fight."
Labour accused the Government's attempts to bring in a new contract for junior doctors of being in "complete disarray".
Shadow health minister Heidi Alexander said: "Jeremy Hunt needs to urgently clarify whether or not he has the powers to impose a new contract. And if not, the Tories are going to have to answer to the thousands of patients and staff who have suffered months of distress and uncertainty because of the decisions they have taken."
According to The Guardian, Justice for Health received a letter from the Government that outlined the change in Mr Hunt's approach.
The group crowd-funded their legal campaign and have so far raised £135,000 to pay lawyers to act on their behalf.
A spokeswoman for the campaign group said their High Court case is likely to be heard in early June.
The new contract is part of the Government's drive to improve care over weekends after its research suggested mortality rates were higher. The DH highlighted that it will not be imposed on NHS foundation trusts, which are free to determine their terms of employment.
Mr Hunt tweeted on Sunday: "As set out in BMA's own FAQs on legal position. Govt done what entitled to following disappointing & needless refusal to negotiate by BMA."