The contract dispute between the British Medical Association (BMA) and the government dates back to 2012 when the Department of Health called for changes to terms and conditions agreed in the 1990s. Talks broke down in August when the BMA's junior doctors committee withdrew complaining about the government's "heavy-handed approach".

They said they would not return until the government backed down from its proposal to extend a junior doctor's routine working hours from 60 hours per week to 90 hours. The committee said it was "unacceptable" that working at 9pm on a Tuesday be considered the same as working at 9pm on a Saturday.

The BMA has also insisted that the government does not remove vital safeguards which discourage employers from making junior doctors from working long hours. This would "protect both doctor and patient safety," it said.

Regarding pay for junior doctors, the union also said that there must be a stop to pay "no longer matching with the experience junior doctors' gain through their training".

The Department of Health has rejected any suggestion that doctors will see a reduction in pay under the new contracts. It also stated that under the new proposals the basic salary would be "around 15% higher than it is now".

Currently, trainee doctors start on Foundation Year One – their first year of training – with a salary of just over £22,000, which rises to £30,000 within four years. Doctors undergoing training towards a speciality can earn between £30,002 and £47,175, which eventually rises to £69,325.

With supplements for weekend, overnights and other work, the Department of Health estimates that a junior doctor under training can earn an average of £40,000 in the initial stages of training and £56,000 in the later stages.

However, before beginning this training, a trainee doctor must hold a medical degree, which can take up to five to six years to earn. According to the National Union of Students, studying for a degree in England costs at least £10,000 a year.

Critics say an end to automatic pay progression could affect doctors who take time out of training to do things like work towards a PhD, as pay is now proposed to rise in line with experience.

The BMA also says that under these proposals doctors who change their speciality "would have to start again from the bottom of the pay scale, meaning a potentially significant pay cut for trainees who may have mortgages to pay or families to support".

Disputing this, the government has said the changes will "incentivise junior doctors to train up and work". It will also stop a doctor's pay from progressing if they fail to continue with training.

If the BMA does not return to the negotiating table, the government has said it will impose the contracts on the NHS in August 2016.