The Health Secretary is facing a second legal challenge by junior doctors to try to block the imposition of "toxic" new contracts.
The NHS staff campaign group Just Health has raised a record £100,000 over four days through a crowdfunding website to bankroll the fresh legal action against Jeremy Hunt.
Lawyers for the group argue that Mr Hunt has no legal right to force the new contract on the majority of junior doctors, and that he has not properly consulted all relevant parties.
Just Health calls the controversial contracts "toxic" and unsafe for doctors and patients.
Dr Francesca Silman, from the group, said: "We hope this legal challenge will hold the government to account, for imposing a contract that threatens the future stability of the NHS."
Just Health was set to deliver a "letter before action" to the Department of Health on Monday morning.
Mr Hunt is already facing a legal challenge from the British Medical Association (BMA) over the contracts.
The BMA argues the government has failed to "pay due regard" to the equalities impact of the new contracts.
"There is no evidence that it will deliver a safer system or better quality care for our patients; it will instead exacerbate the staffing crisis we are already struggling with across the NHS," it said.
On 26 and 27 April junior doctors will take all-out strike action, including the withdrawal of emergency care.
What has prompted the first junior doctors' strike in 40 years?
- Junior doctors are objecting to a new contract in England that the government says will create a truly seven-day service
- They are currently paid more for working unsocial hours at night or at the weekend. But under the proposed new contracts, the Saturday day shift will be paid at a normal rate in return for a rise in basic pay
- They say that the NHS is already understaffed but because the government wants to fulfil their manifesto pledge of a "7-Day" NHS they are putting doctors and patients at risk