Police could visit people’s homes to check they are self-isolating under new coronavirus laws that come into force on Monday.
As well as tough fines for failure to self-isolate, new local lockdowns and further restrictions are being applied across the UK.
People across England will be legally required to self-isolate from Monday if they test positive for coronavirus or are contacted by the test and trace service.
Watch: What are the fines for breaching self-isolation? Find out here
If they do not, they risk being hit with new fines starting at £1,000 and increasing up to £10,000 for repeat offenders or serious breaches, the Department of Health and Social Care (DHSC) said.
People who test positive for COVID-19 will also be fined if they knowingly provide false information about close contacts to the test and trace service.
The DHSC said police will check compliance in the highest incidence areas and in high-risk groups based on “local intelligence”.
High profile and “egregious” cases of non-compliance will be investigated and prosecuted, while action will be taken on tip-offs from “third parties” about people who have tested positive but are not self-isolating, the DHSC added.
A DHSC spokesman told Yahoo News UK: “Local authorities will focus on the principle of encouraging, educating and supporting self-compliance.
“Where there is clear evidence that someone is not following the rules, the police will determine what follow-up action to take.”
Under new rules in England, wedding ceremonies will also be restricted to 15 people.
Meanwhile, three more council areas in south Wales will go into local lockdown from 6pm on Monday, the Welsh government has announced.
Neath Port Talbot, Torfaen and the Vale of Glamorgan will be covered by the restrictions, which mean people will not be able to enter or leave the areas without a reasonable excuse.
They will not be able to meet indoors with anyone they do not live with.
Restrictions are already in place in Cardiff, Swansea, Llanelli, Blaenau Gwent, Bridgend, Caerphilly, Merthyr Tydfil, Newport and Rhondda Cynon Taf.
It comes after bans on households mixing came into force in Wigan, Stockport, Blackpool and Leeds on Saturday, while stricter rules are already in force across large swathes of north-west England, West Yorkshire, the North East and the Midlands, as well as parts of west Scotland.
The new restrictions in three areas of Wales means an estimated 17.8 million people across the UK will be living under additional coronavirus measures by Monday evening, on top of those previously announced.
Health secretary Matt Hancock said: “We all have a crucial part to play in keeping the number of new infections down and protecting our loved ones.
“As cases rise it is imperative we take action, and we are introducing a legal duty to self-isolate when told to do so, with fines for breaches and a new £500 support payment for those on lower incomes who can’t work from home while they are self-isolating.
“These simple steps can make a huge difference to reduce the spread of the virus, but we will not hesitate to put in place further measures if cases continue to rise.”
Watch: What is the new job support scheme?
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