The British Medical Association has already staged two 24-hour walkouts this year, causing some 6,000 planned operations to be cancelled, although emergency care was maintained.
Health secretary Jeremy Hunt then announced he will impose a new pay contract on the staff after talks failed.
The doctors’ union leader Johann Malawana claims further industrial action is “inevitable”.
The contract cuts the number of weekend hours for which junior doctors can claim overtime, by classing 7am to 5pm Saturdays as normal working hours.
Mr Hunt says the system, to improve weekend hospital staffing to reduce patient deaths, makes most staff better or no worse off, and less likely to be overworked.
But the BMA claims it will raise workloads, endanger patients, and junior doctors (qualified medics below consultants) will quit the NHS.
The union’s Junior Doctors Committee (JDC) met on Saturday. Further action, including withholding emergency care, was not ruled out although some fear more walkouts could alienate a currently supportive public.
A legal challenge to Mr Hunt is possible.
Mr Malawana told BMA members: “JDC has made the clear decision that further industrial action is inevitable and that we will consider escalating any action to achieve our aim to end the imposition.
“We also know – and the public understand this – that if the Government wants junior doctors to take the brunt of delivering more services across seven days, they need to put their money where their mouth is.”