The date by which health workers need to have had a mandatory Covid vaccination should be pushed back, the Royal College of GPs has urged.
In order to continue in frontline roles, NHS staff must have received a first dose by February 3 and be fully vaccinated by April 1.
Demonstrations were held across England - including a protest in central London - by NHS workers opposed to the Government's policy of compulsory vaccination.
A Department of Health and Social Care spokesperson said: "Ensuring staff are vaccinated is the right thing to do to protect patients and those in care."
But Martin Marshall, chairman of the Royal College of GPs, told the BBC that mandatory jabs for health workers in England were "not the right way forward."
Taking unvaccinated staff out of frontline jobs by April 1 would lead to "massive consequences" for the NHS, Mr Marshall said, adding that a delay would give more time to administer booster injections.
He also said relaxing the deadline would allow for a "sensible conversation" about the principle of mandatory vaccines.
However, the Department of Health said a delay was not planned and its approach was "the right thing to do to protect patients".
Saffron Cordery, the deputy chief executive of NHS Providers, said a delay was not the answer.
She said: "The last thing trust leaders want to do is further deplete the workforce by dismissing their staff, but they are obliged to implement the law."
And Danny Mortimer, deputy chief executive of the NHS Confederation, said any frontline staff who chose not to be vaccinated would have to leave their jobs.
"This will reduce frontline NHS staff numbers even further and lead to more gaps in capacity at a time of intense pressure and patient demand," he said.
Dr Nikki Kanani, medical director of primary care for NHS England, called on those who took part in the protests to "think about the people you've been looking after who have experienced Covid."
"Think about your colleagues who you've been working with, and think about the best way to make sure that we're all protected, and that we're all as safe as possible, because we are very much in this together and it's down to us to look after each other too," she said.
This week the Prime Minister Boris Johnson told the House of Commons that the Government would "reflect on the way ahead."
He said: "We don't want to drive people out of the service."
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