The Academy of Medical Royal Colleges said it was “disappointed” and the proposed strikes were disproportionate.
The British Medical Association said it was “absolutely behind” the action.
The move escalates what has become the worst industrial relations dispute in the history of the NHS.
Hospitals will see junior doctors stage walkouts from 08:00 to 17:00 BST from:
- Monday 12 September to Friday 16 September
- Wednesday 5 October to Tuesday 11 October (although the weekend will be covered)
- Monday 14 November to Friday 18 November
- Monday 5 December to Friday 9 December
BMA junior doctor leader Dr Ellen McCourt said the government could stop the strikes by calling off the imposition of the contract, which is due to be rolled out from October.
She said junior doctors still have “serious concerns” with the contract.
“The government has consistently said this is about creating a seven-day NHS, when junior doctors already work weekends and it’s been shown that the government has no answer to how it will staff and fund extra weekend care.”
However, many leading health bodies have said the strikes should be called off. The action threatens to cause chaos in the lead-up to winter – the busiest time of year for the NHS.
Simon Paterson Brown, a council member of the Royal College of Surgeons of Edinburgh, which represents more than 10,000 doctors in England and Wales, told the BBC there said there should be on-going negotiations – not strikes.
“All industrial action at any time is likely or has the potential to endanger patients’ safety.
“Obviously with advance notice and short term industrial action these can be mitigated to an extent. But if we could manage the health service without the trainees then we would be doing so already.”
The Academy of Medical Royal Colleges said in a statement: “We know there are genuine concerns about the contract and working arrangements, but we do not consider the proposed strikes are proportionate.
“Five days of strike action, particularly at such short notice, will cause real problems for patients, the service and the profession.”
Kathy McLean, executive medical director at NHS Improvement, also questioned the decision to strike, urging junior doctors to call off the walkouts.
Health Secretary Jeremy Hunt described this month’s strike as “devastating news”, predicting it would lead to the cancellation of 100,000 operations and one million appointments.
Prime Minister Theresa May called on doctors to stop “playing politics” in the dispute and urged the union to cancel the strikes.
Meanwhile, Nigel Edwards, chief executive of independent health charity the Nuffield Trust, said the latest strikes would be significant for senior hospital staff, who stepped in for junior doctors during the last strikes.
He told BBC Radio 4’s Today programme the action could also have a long-term impact on hospitals, which could lose funding because of cancellations.
“They are all in quite serious financial trouble and if they lose three weeks’ worth of planned care income, that is a big deal.”
Katherine Murphy, of the Patients Association, said she was “gravely concerned” about the prospect of five days of strikes, which would have a “catastrophic impact”.
Simon Emmott has a kidney stone and is waiting for surgery.
“I can’t see that the strikes won’t delay my surgery. There are only two people at the hospital that can carry it out, meaning I already have a four-week waiting time.
“I’ve been to A&E with abdominal pain twice in the last week. I constantly feel nauseous and I’m in constant pain. I have to take very strong painkillers which make me drowsy.
“I work from home as an IT consultant and I have to balance taking enough painkillers so I can work through the pain, but not so many that I’m too dopey to work.
“I’d really like to believe the doctors have the patients’ best interest at heart but it doesn’t seem right. They’ve been arguing about this for three years.”
But Prof Neena Modi, president of the Royal College of Paediatrics and Child Health, told the Today programme her college was supporting junior doctors and had no concerns about the safety of patients during the strikes.
“To my best knowledge, I know of no instance of any children who were harmed during the last strikes,” she said.
“I have absolute confidence that my consultant colleagues and all of the other doctor groups, and indeed those trainees who choose not to strike, will actually rally to ensure that patient safety is place first and foremost.”
Hamed Khan, a GP in south London and a member of the BMA national council who voted in favour of the strikes, said the public “appreciates that [junior doctors] have patients’ interests at heart”.
“I think they also appreciate that junior doctors work incredibly hard,” he added.
Labour leader Jeremy Corbyn said Mr Hunt should stop treating NHS staff as the “enemy”.