There are no plans to make face coverings mandatory for office workers in England, Matt Hancock has said.
The health secretary told BBC Breakfast people working in offices will not need to cover up, despite a newspaper report suggesting they would have to.
“It is something we’ve looked at and rejected,” he said, but added masks would be worn elsewhere by the public “for the foreseeable future”.
Face coverings in shops will become mandatory in England on 24 July.
Scotland already requires shoppers to cover their faces while Wales and Northern Ireland are both weighing up similar policies.
Mr Hancock said coverings help prevent spread during brief encounters with strangers, but that social distancing and hand washing are more effective for contact with people over long periods of time.
There is a difference between visiting a shop for a few minutes and working alongside colleagues at a desk for several hours, he said.
“When you’re in close proximity with somebody that you have to work closely to, if you’re there for a long time with them, then a mask doesn’t offer that protection.
“The same logic applies for schools – we’re not recommending masks for schools because if you’re in a classroom with kids all day then a mask doesn’t give you protection.”
Mr Hancock said face coverings were effective “in a shop or public transport, for instance, when you’re with somebody for a reasonable amount of time – a few minutes – but not all day.”
“The point is when you’re in interaction with people who you aren’t normally with, that’s where the mask may be particularly helpful.”
He added: “We are not proposing to extend masks to offices.”
Mr Hancock’s comments came as a council in Blackburn, Lancashire, told residents they must wear face coverings while in all public settings as it worked to combat a “rising tide” of coronavirus cases.
Prof Dominic Harrison, Blackburn with Darwen’s director of public health, said he hoped the use of coverings alongside other specific measures would prevent a Leicester-style local lockdown in the area.
Leicester became subject to the UK’s first local lockdown on July 4 following a spike in Covid-19 cases. There are limits on social gatherings and hotels, pubs and restaurants have not been allowed to reopen.
Meanwhile, questions continue to be asked about the use of masks by politicians.
Speaking on BBC Radio 4’s Today programme, Mr Hancock said he was “not frankly interested” in photographs showing apparent differences in the use of face coverings by cabinet ministers.
Pictures of Cabinet Office Minister Michael Gove showed him without a face covering while buying food at a branch of Pret on Tuesday, while Trade Secretary Liz Truss was seen in the same shop minutes later wearing a bright blue mask.
Mr Hancock said: “Those photographs were taken before I announced the change in policy to the House of Commons yesterday afternoon.
“And it’s absolutely straightforward that from July 24 we’re making it mandatory to wear a face covering in a shop in the same way it’s mandatory on public transport and in the NHS.”
Mr Hancock said the public needed to get used to wearing face coverings in shops and at NHS facilities “for the foreseeable future”.
“People have got to play their part,” he said.
It comes after it was announced those who fail to comply with the new rules on wearing face coverings in England’s shops will face a fine of up to £100.
Children under 11, those with certain disabilities, and people working in shops will be exempt.
Mr Hancock told the Commons on Tuesday the new rule would “give people more confidence to shop safely and enhance protections for those who work in shops”.
Mask-wearing has been compulsory on public transport in England and at NHS facilities across the UK since 15 June.