4,000 operations have been cancelled and patients warned to stay away as thousands of junior doctors around the UK have begun a 24-hour strike

Thousands of Junior Doctors across Britain are striking against proposed changes to their contracts which could see them working longer hours for less pay.

Junior doctors, or doctors in training who represent just over half of all doctors in the National Health Service (NHS), said on Monday they would stage a 24-hour stoppage next week, followed by two further 48-hour strikes.

The government expects some 4,000 non-emergency operations to be cancelled during the stoppage.

Doctors’ strikes are rare in Britain. The last time junior doctors took industrial action was in 1975 over non-payment for work done outside the standard 40-hour working week. A new contract was agreed the next year.

The British government said it was seeking to hold talks with doctors in its state-funded health service in a last-ditch bid to avert a series of mass walkouts, potentially the first such strikes for four decades.

Prime Minister David Cameron issued a last-minute appeal on Monday for the action to be called off. “This strike is not necessary, it will be damaging,” he said at an event in London.

“We will do everything we can to mitigate its effects but you cannot have a strike on this scale in our NHS without real difficulties for patients and potentially worse.”

A British Medical Association (BMA) spokesman urged Junior Doctors to continue with industrial action until NHS England has confirmed, and the BMA has agreed, that a “major unpredictable incident” is taking place.

Dr Roger Stedman, medical director at Sandwell and West Birmingham Hospitals NHS Trust, said: “Over the last two days we have had very high numbers of patients come to hospital, and fewer than usual discharged.

“Because of that we decided to require trainee doctors allocated to ward work to attend Sandwell during today’s strike.”

But a spokesman for the BMA said: “Junior doctors should continue with industrial action until NHS England has confirmed, and the BMA has agreed – via the agreed escalation process – that a major unpredictable incident is taking place for a specific trust.

“The BMA will notify members as soon as such an incident is in place.”

Young medics say they have been threatened with referral to the General Medical Council (GMC) watchdog if they fail to turn up to work today because they are manning the picket lines.

Doctors from St Thomas' Hospital in London wore their medical scrubs as they protested opposite UK Parliament.

Doctors from St Thomas’ Hospital in London wore their medical scrubs as they protested opposite UK Parliament.