A cross-party plan to try and avert the looming junior doctors' strike has been dismissed by Health Secretary Jeremy Hunt as "opportunist".
A rainbow coalition of MPs, including Labour shadow health secretary Heidi Alexander, urged Mr Hunt to test the contested new work contract in a small number of trusts rather than impose it across England without the support of the British Medical Association (BMA).
However, the Health Secretary insists that the contract is already being rolled out slowly.
Mr Hunt tweeted: "Labour 'plan' is opportunism - only 11% of junior docs go onto new contracts in August".
In a letter to BMA chairman Mark Porter, Mr Hunt said: "The extreme action planned will be deeply worrying for patients and place enormous additional strain on our NHS at a time of intense pressure.
"I therefore appeal to you one final time to call off strike action that will see doctors withdraw potentially life-saving care, and to meet with me on Monday to discuss a better way forward."
Ms Alexander, Conservative Dr Dan Poulter, Lib Dem Norman Lamb and the SNP's Dr Philippa Whitford said in a letter to Mr Hunt that they want an independent evaluation of the so-called "weekend effect" which sees higher mortality rates for patients admitted at weekends.
A BMA source said that if the Government agreed to limited trials of a pilot of the contract, representatives would be prepared to meet them to discuss the possibility of calling off the strike on Tuesday and Wednesday.
The MPs wrote: "You will be aware that medical leaders, royal colleges and patient groups have said the imposition or unilateral introduction of the contract is the wrong approach and risks permanent damage to the future of the medical workforce.
"If it remains your intention to introduce this new contract, we believe it should be piloted in a number of trusts/across a number of deaneries and for its impact on patients, staff and the 'weekend effect' to be independently evaluated."
Ms Alexander told Murnaghan on Sky News: "I think Jeremy Hunt would need to sit down urgently today, this afternoon, with the BMA, to talk about what the scope of the pilot would be."
She added: "If it is shown to improve patient care and to have a positive impact upon junior doctors with regard to the hours they are working and the quality of care that they are able to provide, I think any reasonable person at that point would say, well actually, we need to look at what the evidence shows us and move forward in a constructive way."
But the Government said it had 75 meetings with the BMA and three years of talks, and delaying reform further would mean not taking an important step in improving weekend care.
A spokesman said: "We have always said that we want to introduce this contract in a phased way - for around 11% of junior doctors from August - precisely so any initial problems can be ironed out. That's why this is simply ill-informed political opportunism from the same Labour Party responsible for the flawed contracts we have now?."