Surgeons are being advised "not to risk their health" by working without adequate personal protective equipment (PPE) amid fears that hospitals could run out of supplies this weekend.
The Royal College of Surgeons of England (RCS) said it was "deeply disturbed" by changes to official guidance, which now states healthcare professionals could be asked to reuse items when treating Covid-19 patients.
NHS Providers said on Saturday afternoon that the supply of clinical gowns was now "critical", whilst unions leaders warned faith in Health Secretary Matt Hancock is "draining away" over the shortage in supplies.
On Friday evening, Public Health England (PHE) reversed its guidance which stipulated that long-sleeved disposable fluid repellent gowns should be worn.
If the gowns are not available, clinical staff are now advised to wear "disposable, non-fluid repellent gowns or coveralls" or "washable surgical gowns", with aprons, and to wash their forearms afterwards.
The updated guidance states that the "reuse of PPE should be implemented until confirmation of adequate re-supply is in place", and that "some compromise is needed to optimise the supply of PPE in times of extreme shortages".
Professor Neil Mortensen, president-elect of the RCS, said the updated guidance implied that surgeons may not require adequate PPE, which he called "simply unacceptable".
He said that like all doctors, surgeons are committed to their patients and "many will put themselves in the firing line" during the crisis.
But Prof Mortensen echoed advice from the Royal College of Nursing (RCN) that says nurses should refuse to treat patients "as a last resort" if they are not provided with adequate equipment.
"If fluid repellent gowns or coveralls are not available, then surgeons should not risk their health," he said in a statement.
A Department of Health spokesman said on Friday: "New clinical advice has been issued today to make sure that if there are shortages in one area, frontline staff know what PPE to wear instead to minimise risk."
The Government has been under fire for weeks over the distribution of PPE, with some frontline staff warning that they have had to work in situations where they feel unsafe.
NEW: Today's statement on the latest @PHE_uk#PPE guidance.
We are calling on government to ensure that the depleted PPE supplies that remain, are used to maintain the most urgent and emergency services, Read in full: https://t.co/ngj72XzJn9@mortensen_neilpic.twitter.com/YDVTiCBkFg
— RCollege of Surgeons (@RCSnews) April 18, 2020
At least 50 NHS workers have now died after contracting coronavirus.
A British Medical Association (BMA) survey of more than 6,000 doctors across the country said a significant amount of them remain without the protection they need to guard against Covid-19.
It echoed another survey of 14,000 medical staff by the RCN, which found half of nurses have felt pressure to work without appropriate protective equipment during the crisis.
Saffron Cordery, deputy chief executive of NHS Providers, which represents hospital trusts, said on Saturday that the supply of clinical gowns was critical, calling it an "extremely worrying situation".
"The absolute priority is for frontline staff to be able to feel safe and have access to the best possible PPE available," she said in a statement.
"Trust and national leaders have been working around the clock to secure supplies of gowns, but the stock is just not yet available in the quantities needed."
She said the new guidance on PPE usage to manage the shortage is endorsed by the World Health Organisation (WHO).
A total of 15,464 patients have died in hospital after testing positive for coronavirus in the UK as of 5pm on Friday, the Department of Health said, up by 888 from 14,576 the day before.
On Saturday, a key adviser to the Government on the disease said trials for a vaccine could be completed by mid-August.
Professor Sir John Bell, a member of the Government's vaccine task force and an adviser on life sciences, told BBC Radio 4's Today programme that it "reasonable to think" that they would be able to complete their trial within this time-frame.
Elsewhere, senior Tory MPs have accused ministers of underestimating the public by refusing to discuss exit strategies for ending the coronavirus lockdown.
Former Brexit secretary David Davis told the PA news agency: "There are lots and lots of benefits of being open about this.
"The argument that was put, that we don't want to confuse the message, I think is just wrong.
"It underestimates the public. The public understand that there are phases to this."