Concerns have been raised that updated government guidance on personal protective equipment (PPE) could put hospital staff and patients at risk.
Healthcare workers have been advised to reuse gowns or wear different kit if stocks in England run low.
Unions representing doctors and nurses have expressed concerns about the updated Public Health England guidance.
It comes as the UK recorded another 888 coronavirus deaths, taking the total number of hospital deaths to 15,464.
There have been warnings some hospitals could run out of the gowns used in intensive care units this weekend. The government said it is working to provide the PPE stocks hospitals need.
Healthcare staff treating patients with Covid-19 have previously been advised to wear long-sleeved disposable fluid-repellent gowns.
But Public Health England changed its guidance on Friday, outlining three options if the gowns are not available as "some compromise is needed to optimise the supply of PPE in times of extreme shortages".
One option is for hospitals to reserve the gowns for surgical operations and procedures which are likely to transmit respiratory pathogens.
Another is for staff to reuse "(washable) surgical gowns or coveralls or similar suitable clothing (for example, long-sleeved laboratory coat, long-sleeved patient gown or industrial coverall) with a disposable plastic apron for AGPs (aerosol-generating procedures) and high-risk settings with forearm washing once gown or coverall is removed".
Front-line workers are particularly at risk. The British Transport Police has announced that a 53-year-old detective has died with coronavirus, leaving behind a wife and child.
Greater Manchester Police announced that Marcia Pryce, 61, who worked in the force's intelligence bureau, died after contracting Covid-19.
Meanwhile, councils in England have warned that the coronavirus crisis is pushing them to the brink of financial failure.
Elsewhere, Buckingham Palace has confirmed the Queen will not be marking her 94th birthday next Tuesday with gun salutes this year.
'Lives on the line'
There have been warnings that trusts across England will run out of PPE over the weekend.
Chris Hopson, chairman of NHS Providers, which represents healthcare trusts across England, said in a tweet: "We have now reached the point where the national stock of fully fluid-repellent gowns and long-sleeved laboratory coats will be exhausted in the next 24 to 48 hours."
He said that national leaders have left "no stone unturned" - but the gowns are made in China and those that were ordered weeks ago are currently only arriving in "fits and starts".
The Royal College of Nursing said the guidance was developed without a full consultation and the British Medical Association (BMA) - which represents doctors - said any change must be driven by science, not availability.
Dr Rob Harwood, consultants committee chairman at the British Medical Association, said: "Too many healthcare workers have already died.
"More doctors and their colleagues cannot be expected to put their own lives on the line in a bid to save others, and this new advice means they could be doing just that. It's not a decision they should have to make."
Dr Harwood added: "It's a real disappointment to us that the government has been unable, even after a month, to address this progressively worsening shortage of PPE."
Unison, the UK's largest trade union, has warned that staff in "high risk areas" might refuse to work if gowns run out.
Prof Neil Mortensen, from the Royal College of Surgeons of England, said surgeons should "not risk their health" if fluid repellent gowns or coveralls were not available.
He said he was "deeply disturbed" by the new guidance, which, he said, implied that "even in the operating theatre" surgeons and their teams may not require proper PPE.
A Department of Health spokesman said: "New clinical advice has been issued today to make sure that if there are shortages in one area, front-line staff know what PPE to wear instead to minimise risk."
The spokesman added the advice is in line with World Health Organization and Centers for Disease Control guidance on PPE use in "exceptional circumstances".
Niall Dickson, chief executive of the NHS Confederation, representing health service trusts, said the situation was "worrying" and "less than satisfactory".
He told BBC Radio 4's Today programme: "The reality is that there is a chance, and I don't think it's definite, but there is a chance that hospitals could run out or, indeed other parts of the system could run out of the gowns which are required to treat some, not all, Covid patients."
Meanwhile, former Conservative leader Sir Iain Duncan Smith said the government needs to "bring the British people into its confidence" over how it plans to end the lockdown.
"People have done what they were asked with good humour and common sense," he told BBC News, adding that businesses in particular needed clarity.
Jonathan Blake, political correspondent
In a sign of growing frustration at the lack of detail from the government about how it plans to end the lockdown, Conservative MPs are adding their voices to the calls for clarity.
Senior figures on the backbenches have gently suggested that ministers need to do more to explain when and how restrictions on our daily lives may end.
The government says any talk of lifting the lockdown would distract from the critical message for people to stay at home in order to slow the spread of the virus.
But Tory MPs are joining Labour and others who say people are capable of doing that while being kept informed about the eventual return to something like normality.
Downing Street has acknowledged that there is a debate taking place across government departments about how an exit strategy might work, when the time comes.
But while ministers insist they are guided by scientific and medical evidence, the political decision to move towards lifting the lockdown may have to wait until the prime minister has recovered and is able to return to work.
In other developments:
- The World Health Organization questioned whether antibody tests will offer any guarantee of immunity against coronavirus
- Testing will be rolled out to people working in public services such as police, fire and prison staff, the health secretary has said
- Scientists at the University of Oxford said they should have at least a million doses of a coronavirus vaccine by September
- Councils in England warned that the coronavirus crisis is pushing them to the brink of financial failure
- Chancellor Rishi Sunak extended the government's furlough scheme by another month until the end of June
- Four charter flights will depart between Tuesday and Sunday from Bangladesh to take up to 850 British nationals home, with priority being given to vulnerable passengers most at risk of coronavirus
- Providing hotel rooms for those sleeping on England's streets should lead to a long-term reduction in rough sleeping, says a charity supporting the homeless
- A star-studded concert to support frontline workers featuring artists including the Rolling Stones and Billie Eilish will be live-streamed and broadcast on TV
- US President Donald Trump has defended his tweets after appearing to endorse protests against lockdown measures in several US states