Former health minister and Lib Dem health spokesman Norman Lamb has said that the key problem in the dispute between junior doctors and the government over new contracts is down to a "chronic financial crisis" in the NHS.
"More strikes could be very damaging given that services are already under intolerable pressure," he said.
"I therefore repeat my call to the Government to agree to an urgent cross-party process aimed at achieving a new settlement for the NHS and care.
"There's no reason why we can't achieve a modern, highly effective NHS and care system but the government will have to work with others to achieve that."
The Academy of Medical Royal Colleges has said it is "disappointed" at the prospect of further industrial action each month until the end of the year.
In a statement, it said: "We are acutely aware that the NHS is under extreme pressure at the moment. Patient safety and quality of care must be the priority.
"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."
The British Medical Association has announced further strikes in addition to the ones in September announced on Wednesday.
The additional strike dates are October 5, 6, 7, 10, and 11, November 14-18, and December 5-9, and will take place only in England.
Theresa May has said that the deal on the table between the government and the BMA is a deal "that is safe for patients."
The Prime Minister cited "record levels of funding in the NHS" and more doctors in the NHS than in its history.
She reiterated that the BMA should put patients first, "not playing politics".
The council chairman of the British Medical Association (BMA) has backed the forthcoming doctors strike and rubbished claims his organisation were split on supporting the decision.
Reports on Thursday suggested BMA members backed industrial action by a narrow 16-14 split.
However its council chairman, Dr Mark Porter, said: "The council is absolutely behind, as is the rest of the BMA, absolutely behind the decision that has been taken. There is no split - that is a made-up story."
He added: "This is a misrepresentation, there are not a considerable number of members of council who don't support this."
Prime Minister Theresa May has accused the British Medical Association (BMA) of "playing politics" instead of "putting patients first".
She said the deal was "safe for patients", adding that the NHS had "record levels of funding" and "more doctors than we've seen in its history".
Mrs May also gave Health Secretary Jeremy Hunt her backing, saying he was an "excellent health secretary".
Junior doctors will hold five days of strikes, lasting from September 12 to 16, in the continuing row over new contracts.
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Health Secretary Jeremy Hunt has said the forthcoming strike by junior doctors is both "perplexing and disappointing".
Speaking to Good Morning Britain on Thursday, he said: "It's devastating news for many people. It's going to cause a lot of misery for a lot of people.
"Our one promise was that we wanted a proper seven-day service, so [people] can be confident no matter what day of the week they're admitted to hospital, they're going to get the same high quality care.
"We have an honest difference of opinion with them about how to deliver that seven-day service, but the way to resolve that difference is to sit around the table and talk.
"It's cooperation and dialogue, not confrontation and strikes... I thought we were making progress, and that's why I find it so perplexing and disappointing to see that we're going to have to deal with this huge strike."
The junior doctor strike represents a "serious escalation" of the ongoing dispute and is a "great concern", according to the head of the General Medical Council (GMC).
Niall Dickson, chief executive of GMC, said: "It is obviously a matter of great concern for everyone, especially for patients, and when so little time has been given for the NHS to make contingency plans.
"We recognise the frustration and alienation of doctors in training and indeed their right to take industrial action. However, we issued advice earlier in this dispute both to senior doctors and doctors in training, and we will now consider whether further guidance is needed."
He added: "The first priority must be to protect patients from harm.".
A five-day strike by junior doctors has been called in the ongoing dispute over contracts, but what does it mean for patients?Read the full story ›