Plans to make face coverings compulsory on public transport do not go far enough, the British Medical Association has warned.
From 15 June, bus and train commuters in England could be refused travel if they fail to comply with the measures - or face a fine.
But according to the BMA, this should be extended to all areas where social distancing is not possible.
BMA council chair Dr Chaand Nagpaul also questioned why the introduction of these measures has been delayed - adding that the risk posed by coronavirus would be "much less" if the public starts wearing face coverings immediately.
He said: "The BMA recently advocated the wearing of face coverings by the public several weeks ago in areas where they cannot socially distance and believes it is right that people should be required to wear face coverings on public transport.
"Given there remains a considerable risk of infection, with thousands of new cases every day, wearing masks can reduce the spread of the virus.
"Not only will this afford greater protection to the public, importantly it will protect the lives of the staff working on public transport who, as evidence suggests, are at greater risk of infection."
Dr Nagpaul has also called for the government to provide a supply of face coverings to the public, and offer advice on how they can be used correctly.
BMA Wales council chair Dr David Bailey also pressed the Welsh government to change their position on face coverings to make them mandatory.
The Welsh government has said the use of face coverings is "a matter of personal choice" for the public.
Face coverings can include scarves, a piece of cloth or a mask - and certain travellers, such as young children and people with disabilities or breathing difficulties, will be exempt.
At the moment, passengers are advised to wear a face covering but are not prevented from boarding transport without one.
Announcing the plans, Transport Secretary Grant Shapps said "we need to ensure every precaution is taken" as England relaxes the lockdown further, and passenger numbers start to increase once again.
The government says face coverings are "marginally beneficial as a precautionary measure".
It's coronavirus guidance states: "Evidence suggests that wearing a face covering does not protect you.
"However, if you are infected but have not yet developed symptoms, it may provide some protection for others you come into close contact with."
According to official advice, surgical masks should be reserved for people who need them for protection while at work.
London mayor Sadiq Khan, who has been lobbying ministers to make face coverings mandatory, welcomed a government "u-turn" on the issue.
He told Sky News: "I don't understand why it's taken this long for the government to reach it's view in relation to making it compulsory.
"I think that should be extended to shops as well.
"Not because we're encouraging people to break the two metre rule, but because... this is another step we can take to mitigate the chances of catching the virus or passing it on."
Asked why face-coverings were being made compulsory on public transport but not in other settings, such as supermarkets, Mr Shapps told Sky News: "The big difference on public transport is that you'll likely to be stuck in a space for a longer period of time, whereas in a supermarket you might go past somebody quite quickly.
"So it is also a factor of the amount of time you spend with somebody.
"On public transport you could be there for 10 to 20 minutes, half an hour or longer, so that actually becomes more important.
"It has been quite a marginal scientific argument, on balance we think that now the trains, buses, trams and aircrafts are likely to be more congested than before, it's a sensible, additional precuationary measure.
"But certainly not a magic, silver bullet thing to do.
"It's also important to note, when you wear a mask, you're actually protecting those around you a bit, as well as yourself.
"So it's quite a public-spirited, altruistic thing to do as well."
Shadow transport secretary Jim McMahon said it was "another example of the government being slow to act", adding: "Two months ago, Labour immediately backed the mayor of London's call for face coverings on public transport to be compulsory.
"Yet only now Tory ministers are acting."
Transport unions echoed the criticism of the government - describing the measures as "long overdue".
RMT general secretary Mick Cash said: "We fear this announcement is being driven not by safety concerns but by the premature easing of the lockdown which is swelling passenger numbers and making social distancing on transport increasingly impossible."