Video report by ITV News Political Correspondent Daniel Hewitt
Coronavirus rule breakers in England could soon face a minimum £1000 fine as it becomes law for those who test positive, or are contacted by Test and Trace, to self-isolate.
Under the new rules, repeat offences - and the most serious breaches - could be punished with fines of up to £10,000.
The crackdown is part of a bid to reduce the recent rising cases of Covid-19, with the Prime Minister warning the UK is facing a "second wave".
Police checks in areas with high rates on infections, fines for those who prevent others from self-isolating, and investigations into reports of rule breakers are all part of the latest measures.
From September 28 people in England will be required by law to self-isolate if they test positive or are told by NHS Test and Trace to do so.
ITV News Political Correspondent Daniel Hewitt has more:
Ministers are in discussion with the devolved administrations for Scotland, Wales and Northern Ireland about extending the rules UK-wide.
Test and Trace call handlers will make regular contact with those self-isolating to check they are doing so.
If someone is thought to be breaking the law, call handlers will be able to escalate the case and raise it with Local Authorities or the police.
Boris Johnson said the shift to "legal obligation" was important in the "fight" against coronavirus.
"The best way we can fight this virus is by everyone following the rules and self-isolating if they’re at risk of passing on coronavirus," he said.
The PM added: "People who choose to ignore the rules will face significant fines.
"We need to do all we can to control the spread of this virus, to prevent the most vulnerable people from becoming infected, and to protect the NHS and save lives."
Sir Keir Starmer has said he supports the move towards fining those who do not comply with self-isolation requirements. He told Sky News’ Sophy Ridge: “Look, I support that. There are a few people that are breaking the rules and something has to be done about that. “I have to say that I think that is not going to be the silver bullet, that isn’t going to deal with the problem we’re in. “We’ve got rising infection rates, I think the whole country is concerned about that, but we have a testing system, just as we need it to be effective, is barely serviceable and this is a major problem.”
What are the new measures?
Under the plans, those on lower incomes and unable to work from home - therefore at risk of losing income by self-isolating - will receive a lump sum payment of £500.
The government says just under 4 million people in England would be eligible for the 'Test and Trace Support’ payment.
The scheme is not expected to be in place until 12 October, however, with those self-isolating from when it becomes law two weeks at risk of facing a shortfall.
Number 10 says for those individuals a backdated payment will be paid once the scheme is set up by the Local Authority.
People preventing others from self-isolating could also be liable for fines under the new rules, for example business owners who threaten impacted staff with redundancy.
As with other Covid rules, there will be exemptions for those who need to escape from illness or harm during their isolation, and for those who require care.
The latest measures come as cases in the UK continue to rise, with 4,442 new positive test results reported on Saturday - the highest day-on-day rise since May.
ITV News also understands that Mayor of London Sadiq Khan is putting pressure on Number 10 to impose a lockdown in London as has been seen in the North East of England.
A mayoral source told ITV News Political Correspondent Daniel Hewitt London "can’t afford more delay."
Adding: "It’s clear that cases in London are only moving in one direction, we are now just days behind hotspots in the North West and North East."
Boris Johnson has faced calls from the First Ministers of Scotland and Wales to bring together a meeting of the government’s Cobra civil contingencies committee to discuss the worsening situation.
Labour's deputy leader Angela Rayner told ITV News her party will "support the government" with further lockdown measures but said she was "incredibly frustrated" that Boris Johnson hadn't "reached out" to communicate with other leaders.
While Professor Neil Ferguson, of Imperial College London - whose modelling led to the original nationwide lockdown - has warned authorities need to act "sooner rather than later" if they are to avoid a return to the infection rates of March.
Ahead of the latest measures being announced, leading doctors called on the government to introduce stricter rules to drive down case numbers and avoid another national lockdown.
The British Medical Association (BMA) said that unless people stick rigorously to social distancing and infection control measures, or there is better enforcement, infection rates will soar.
The group warned the NHS could “once again be crippled” as it tries to cope with the number of patients with Covid-19.