The Government has accused Labour of "ill-informed political opportunism" for urging Jeremy Hunt to agree to trial the new junior doctors' contract in a bid to prevent next week's unprecedented strike.
Labour's shadow health secretary Heidi Alexander is part of a group of cross-party MPs calling on the Health Secretary to pilot the contested contract in a small number of trusts, rather than impose it across England without the support of the British Medical Association.
Doctors' leaders have said they will consider calling off next week's strike if Hunt agrees to limited trials, The Press Association reported.
Ms Alexander, Conservative Dr Dan Poulter, Lib Dem Norman Lamb and the SNP's Dr Philippa Whitford said in a letter that they want an independent evaluation of the so-called "weekend effect" which sees higher mortality rates for patients admitted at weekends.
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."
The cross party MPs wrote to Hunt: "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."
However, Mr Hunt has written to Mark Porter, the chairman of the BMA council, asking him to call off the strike and instead meet him to discuss workforce requirements for seven-day services, improvements in training and improving the work-life balance for junior doctors.
His letter 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."