Retailers and police must both play a role in enforcing the use of face coverings by shoppers in England, a Cabinet minister has said after officers warned the law would be unenforceable.

Environment Secretary George Eustice also defended the delay in introducing the measure to combat the spread of coronavirus as the UK relaxes the lockdown.

Health Secretary Matt Hancock formally announced in the Commons on Tuesday afternoon that anyone failing to comply with the order in England from July 24 could face a fine of up to £100.

Ken Marsh, chairman of the Metropolitan Police Federation, which represents rank-and-file officers in London, warned over the law’s enforcement as he called for shopkeepers to “step up to the plate and take some responsibility”.

“It will be nigh-on impossible for enforcement because you won’t have a police officer on every shop door because there isn’t enough of us,” he told BBC Radio 4’s Today programme.

“If a shopkeeper calls the police because someone hasn’t got a mask on, they haven’t got the power to detain them so that person can just walk away.

“We’ll be driving around and around London looking for people who weren’t wearing masks, it’s absolutely absurd.”

Mr Hancock said shopkeepers “can refuse entry” to people not wearing coverings and said police enforcement would be the “last resort” after the Police Federation of England and Wales pressed on the issues.

As the Government tries to revive the economy, he told MPs the mandatory use of coverings would give the public “more confidence to shop safely and enhance protection” for shop workers.

Earlier in the day, Mr Eustice urged the public to “play their part and to abide by these restrictions”, saying retailers and shoppers both had responsibilities to uphold before the police will be asked to step in.

When it comes to that final sanction of issuing a penalty, that is something that only the police can do

“Of course retailers have been very responsible in the way they’re approaching this challenge, they will have a role to play in making sure there’s compliance,” he told Today.

“But when it comes to that final sanction of issuing a penalty, that is something that only the police can do.”

National Police Chiefs’ Council chairman Martin Hewitt said that, “while we were unaware that the announcement was to be made” to journalists on Monday night, the delay before implementation would give them time to work with the Home Office on the legislation.

“As with other coronavirus regulations, we will follow an approach of engaging, explaining, encouraging and only enforcing where encouragement has been unsuccessful,” he added.

Also raising questions over enforcement, the latest data showed not a single person in England and Wales was fined by police for breaching quarantine rules after arriving from abroad.

And only 10 tickets were handed out to passengers for not wearing face coverings on public transport, the figures released by the NPCC on Friday showed.

JD Sports chief executive Peter Cowgill suggested his stores will offer face coverings to anyone not wearing them but said it will not be for his staff to enforce the law.

“The guidance so far is that our store colleagues are not really to get involved and it’s a police matter to enforce rather than for them to get involved in any potential public disturbances,” he told Today.

Mr Cowgill also criticised the delay to introducing the measure, saying “it will have an impact on consumer confidence” as he blamed ministers for “inconsistencies and the indecisiveness”.

Federation of Small Businesses national chairman Mike Cherry called on the Government to deliver coverings or funding to buy them so customers are not turned away.

Meanwhile, Mr Eustice said they would not be compulsory for shop staff, or in pubs and restaurants, and he defended the delays to introducing the measure.

He told the BBC that ministers want to “give people time to plan and prepare” by delaying the enforcement of the measure until July 24.

The Cabinet minister said the measure, which had been in place in Scotland since Friday, was now backed by the Westminster Government because the evidence “has been evolving”.

The move follows a weekend of confusion over whether ministers intended to make face coverings compulsory after Boris Johnson said they were looking at “stricter” rules.

Senior Cabinet Office minister Michael Gove said on Sunday he did not believe they should be mandatory and that it was better to “trust people’s common sense”.

The Government has been urging people to wear face coverings in confined spaces such as shops since early May and they have already been made compulsory on public transport in England since mid-June.

The regulations will be made under the Public Health (Control of Disease) Act 1984, with a maximum fine of £100 – reduced to £50 if it is paid within 14 days.

As is the case on public transport, children under 11 and those with certain disabilities will be exempt.

For Labour, shadow health secretary Jonathan Ashworth said ministers needed to explain why it had taken them so long to act.

“The Government has been slow and muddled again over face coverings,” he said.