Wearing a face covering on public transport in England will be compulsory from 15 June, the transport secretary has announced.
People with disabilities and breathing difficulties will be exempt, as will young children.
He said “we need to ensure every precaution is taken” on buses, trains, aircraft and ferries as the COVID-19 lockdown is relaxed further and passenger numbers increase.
A face covering can be a scarf, piece of cloth or a mask.
People should wash their hands or use hand sanitiser before one is put on or taken off, while coverings should also be washed regularly.
At the moment, passengers are advised to wear a face covering but are not prevented from boarding transport without one.
Mr Shapps said changes would be made to the conditions of travel for trains and buses, which “will mean that you can be refused travel if you don’t comply and you could be fined”.
“Alongside transport operators, this will be enforced by the British Transport Police if necessary, but I expect the vast majority of people won’t need to be forced into this,” he added.
The government says face coverings are “marginally beneficial as a precautionary measure”.
Evidence suggests they do not protect the wearer, but may protect other people if he or she is infected with COVID-19.
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, said the government has “finally seen sense”.
He added that there is “a large body of evidence” that they can help stop the spread of the coronavirus.
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 have also been calling on Downing Street to enforce the wearing of face coverings, following the deaths of dozens of workers during the pandemic.
Mick Cash, general secretary of the Rail, Maritime and Transport union, said the move was “long overdue”.
Appearing alongside Mr Shapps at the COVID-19 briefing, Network Rail chairman Sir Peter Hendy said he expects most passengers to comply with the new rule.
“I am not expecting a huge upsurge in railway staff having to police this,” he said.
“I am expecting sensible passengers to do their duty and look after themselves and others.”
The transport secretary suggested that passengers on trains starting their journey outside England may have to put on coverings when crossing the border.
But he said it would be up to Scotland and Wales to put out their own guidance.
Mr Shapps said: “Usually what happens, I can say having been through this process in quite a lot of different ways over quite a long period of time with this coronavirus, is you end up finding after some discussion typically the nations decide to move together at roughly the same time.
“So I don’t think it will turn out to be terribly confusing.”
Sir Peter added: “I would expect people who board a train in England to be wearing a mask when they go in the station and on the train and I would expect the passengers to be wearing it when they got off wherever they were.
“And that would be just sensible and it would be protective of both of them and other people and courteous too.”
Nicola Sturgeon, Scotland’s first minister, said in response to the announcement that her government is “considering making it mandatory” to wear face coverings on public transport and in shops.