Train operators have pledged to “support” passengers who continue wearing face coverings if they become voluntary.
Industry body the Rail Delivery Group (RDG) said “wearing a mask helps protect others”, but demanded that any relaxation of the rules around their use indoors must apply to trains.
Boris Johnson is expected to announce on Monday that face coverings will no longer be required from the final step of the Government’s road map out of lockdown, due to take place on July 19.
An RDG spokesman said: “Trains should be treated consistently with other indoor settings when it comes to the removal or ongoing use of restrictions.
“Travelling by train is low risk and carriages are well-ventilated, with air regularly refreshed either by air conditioning systems, or by doors and windows being opened, so any decision to leave public transport behind other parts of the economy would need to be based on the science.
“Of course, train companies will continue with extra cleaning and better information about how busy services are, and, given that wearing a mask helps protect others, we would also support people who wished to continue wearing one in future if it becomes voluntary.”
Even if the Government eases the rule on face coverings on public transport, some operators could make them a condition of carriage.
Greater Manchester Mayor Andy Burnham urged the Government to retain the requirement to wear a face covering in “locations where people don’t have a choice to go”, such as public transport and supermarkets.
But he told BBC Radio 4’s World At One that he would not make them mandatory on Manchester’s tram network as “I just don’t think it would work”.
“If the Government comes up with a national ruling I just don’t see how we would be able to enforce it at our level,” he said.
There's a real danger of the Government making up policy on the hoofMick Lynch, RMT union
The situation in London is complicated by the Government’s recent bail-out of Transport for London (TfL), and the fact that many passengers use a combination of TfL services and mainline rail.
A spokeswoman for Mayor of London Sadiq Khan said: “On the continuing wearing of face masks, it is important that we continue to follow the science around the extent to which they limit transmission on transport and in busy indoor spaces.
“Evidence shows that the wearing of face masks gives many Londoners the confidence that they can travel safely on public transport.
“People feeling confident they can travel on our Tubes, buses and trains as they get busier will be a vital part of encouraging more people into central London as restrictions are lifted further, and it is something that we will continue to look at closely.”
Trade union Unite, which represents tens of thousands of public transport workers, called for face coverings to remain mandatory on public transport.
The union’s national officer for passenger transport, Bobby Morton, said: “To end the requirement to wear masks on public transport would be an act of gross negligence by the Government.
“Rates of infection are continuing to increase and, not only does mask-wearing reduce transmissions, it helps provide reassurance to drivers and to passengers who are nervous about using public transport.
“The idea of personal responsibility and hoping that people will wear masks is absolutely ridiculous.”
Care minister Helen Whately was asked on BBC Radio 4’s Today programme if she would continue to wear a mask when commuting by train from her constituency of Faversham, Kent, to London.
She replied: “I think it’s the sort of environment where, if something’s crowded, I think I might.”
Ms Whately added: “I know personally, and I know others, aren’t comfortable wearing masks all the time.
“As I’ve said, there are downsides to masks as there are downsides to many of the restrictions.”
This comes after Communities Secretary Robert Jenrick was asked on Sky News’ Trevor Phillips On Sunday programme whether he would “get rid” of his mask after July 19 if permitted to do so.
He responded: “I will. I don’t particularly want to wear a mask. I don’t think a lot of people enjoy doing it.”
Mick Lynch, general secretary of the Rail, Maritime and Transport union (RMT), claimed that “yet again there’s a real danger of the Government making up policy on the hoof on critical issues”.