People who use public transport could be fined up to £100 if they do not wear a face covering from Monday, the transport secretary has warned.
From June 15 it will be compulsory for people to wear a face covering when on public transport and operators will be able to "refuse permission to travel" if someone is not wearing one.
Grant Shapps said there will be "gentle approach" to enforcement during first couple of days, but said there will be "fines for non-compliance too".
He told the Downing Street briefing: “Remembering your face covering should be the same as picking up your phone, your wallet or your purse whenever you’re leaving your house.”
He said people should wear face coverings to "protect your fellow commuters" when travelling on the buses, coaches, trams, ferries, aircraft and trains.
The transport secretary said people should only wear coverings - something such as a scarf or a home-made garment - and not clinical face masks, which should only be health professionals.
Hundreds of thousands of face coverings will be handed out for passenger use at many locations across the rail network in England from Monday.
The one-off initiative, which will run for several days at a number of stations, will see coverings provided free of charge to support passengers and help them travel safely.
The police and Transport for London authorised personnel will be able to issue fixed penalty notices of £100, or £50 if paid in 14 days.
Earlier on Friday a German report, published by the Institute of Labour Economics, said compulsory face coverings could “reduce the daily growth rate of reported infections by around 40%”.
Mr Shapps said there was no need for people to wear them in all public settings, just in enclosed spaces.
“By its very nature if you are on a train or a plane or a ferry or a bus you are in an enclosed area.
"That is not the case if you are out and about on the streets. And I think that may be the principle difference of this.”
Sir Peter Hendy, the chairman of Network Rail, said as the economy ramps up with the reopening of non-essential retail from Monday, "there will be more and more occasions in which you might be closer to people than you would care for".
As such, he said it seems "perfectly logical" to enforce face coverings from the same point.
Professor Stephen Powis added that “the evidence is weak" on the effectiveness of face coverings in reducing the spread of coronavirus, but said there is "some evidence" they work.
He said it is "better" for people to wear them in "closed spaces than open spaces where there is less risk of transmission".
Exemptions for the use of face coverings will apply to those with certain health conditions, disabled people and children under the age of 11.
Cab hailing app Uber has followed the government's lead in enforcing face coverings, with all drivers and passengers across the UK being told to wear them from Monday.
The firm’s regional general manager for northern and eastern Europe, Jamie Heywood, said: "As cities begin to reopen and people start moving again, we’re taking measures to help everyone stay safe and healthy every time they use Uber.
“We’ve introduced measures to ensure that every driver can access the PPE (personal protective equipment) they need for free to help keep them safe when driving with Uber, and, from Monday, we will require anyone using the Uber app in the UK to wear a face covering.”
Mr Shapps played down reports that the chief nursing officer for England has been unable or unwilling to take part in the No 10 press briefings because she would not defend Dominic Cummings.
The transport secretary told the Friday briefing that he expected Ruth May would be appearing again at future briefings.
“I don’t think it is true. She has attended them many times before. I notice that at the top of the No 10 Twitter feed I see one of her tweets pinned,” he said.
“I am absolutely sure she has been a regular contributor before and I am sure she will be back here again.”
The Office for National Statistics said economic activity dropped by 20.4 per cent in April - the largest drop in a single month since records began in 1997.
Speaking following the release of the figures, Mr Johnson said he was "not surprised" the UK had been "badly hit" by the lockdown.
Mr Shapps sought to allay concerns that the R value could be above one in the South West of England.
“I think not to be overly alarmed because as Professor Steve Powis said it was actually the top of a range which had a number of others that showed it was below 1.”
Professor Powis said: “R is of course a very important way of looking at this but there are other things that we look at.”
But he said the ONS surveillance study showed a “steady reduction” in the number of infections in the community.
“And really that evidence also suggests the R value is below 1 because it is only when the R value is below 1 that we would see that decrease in infections,” he added.