Health services in Croydon have postponed hundreds of appointments ahead of an "unprecedented" junior doctors strike tomorrow.

The British Medical Association (BMA) announced last month it would be escalating the industrial action to include emergency cover for the first time in response to the Government's "continued refusal" to re-enter talks on controversial contracts.

Junior doctors will withdraw their service in emergency departments for 18 hours between 8am and 5pm on Tuesday to Wednesday.

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Ahead of industrial action tomorrow Croydon Health Services NHS Trust has postponed 806 appointments, 35 operations and 36 endoscopies in preparation for the strike.

Jayne Black, chief operating officer and deputy chief executive at the trust, said: “This is the first time that junior doctors will not be providing emergency cover so we are bringing together all our resources across the Trust to ensure we have clinicians on the floor to care for people should they need emergency care during these two days.

“This has meant we have had to cancel more appointments than during previous disputes. We are very sorry about this and will reschedule these, and any postponed operations, as soon as possible.”

More than a dozen medical leaders have written to Prime Minister David Cameron today calling for him to step in “at the eleventh hour” and bring both parties back to the negotiation table.

The letter said: "You have spoken many times about your commitment to the NHS. In our view, as leaders of the medical profession, the ongoing impasse in the dispute between Government and junior doctors poses a significant threat to our whole healthcare system by demoralising a group of staff on whom the future of the NHS depends.”

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Speaking in the House of Commons this afternoon Health Secretary Jeremy Hunt refused to re-enter negotiations with junior doctors and urged them not to withdraw emergency care.

He said: "The impact of the next two days will be unprecedented with over 110,000 outpatient appointments and over 12,500 operations cancelled.

“I understand the frustration many junior doctors feel that because of pressures on the NHS frontline they are not always able to give patients the highest quality of care that they would like to.

“I understand that some doctors may disagree with the Government over our seven-day NHS plans, particularly the introduction of a new contract.

“I also understand that doctors work incredibly hard, especially at weekends, and that strong feelings exist on the single remaining disagreement of substance: Saturday premium pay.

“But, the new contract offers junior doctors that work frequently at weekends more Saturday premium pay than nurses, paramedics, the assistants that work in their own operating theatres, more than police officers, more than firefighters and more than every other worker in the public sector.

“Regrettably during this pay dispute more than 150,000 sick and vulnerable people have seen their care disrupted.

“The public will rightly question whether this is appropriate or proportionate action by professionals whose patients depend on them.”

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The strike is the third since Health Secretary Jeremy Hunt announced he would impose a new contract by August and claimed the union had refused “point blank to discuss reforms”.

Under the contracts junior doctors will get an increase in their basic pay, but will have to work more weekends. Guaranteed pay rises linked to time in the job will be axed and bonus pay for working unsociable hours will be curbed.

Last week the BMA wrote to Health Secretary Jeremy Hunt saying the union will call off this week’s strike if the Government lifts the “imposition” of the new contracts.

Dr Johann Malawana, chairman of the BMA junior doctors committee said: “The imposition of this contract is tremendously damaging to the morale of junior doctors and medical students and has resulted in a complete breakdown of trust between doctors and the Government.

“It is this decision which has led to the current, lamentable situation, the resolution to which is now squarely in your hands.”

On Saturday, a coalition of MPs including Labour shadow health secretary Heidi Alexander urged Mr Hunt to test the new work contract in a small number of trusts rather than impose it across England without the support of the BMA.

Mr Hunt dismissed the proposal as Labour “opportunism” and wrote to the BMA on the same day urging them to reconsider the strike action.

Anyone feeling unwell during the strike is asked to the NHS on 111 or speak to your GP or pharmacist.

You can also check your symptoms at nhs.uk/strike.