Household mixing in any setting is to be made illegal in large parts of the north east of England as the number of coronavirus cases “continues to rise sharply”.
It was already illegal for two households to mix indoors or in the garden, but until now it was only guidance that they should not meet in public venues such as restaurants and pubs.
It means friends will be breaking the law if they meet up in those premises.
Addressing MPs in the Commons, Health Secretary Matt Hancock said the existing COVID-19 measures were being tightened at the request of local councils.
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The beefing up of coronavirus restrictions will take effect from midnight on Wednesday and will apply to Northumberland, Newcastle, North and South Tyneside, Gateshead, Sunderland and County Durham.
It will be enforceable by law, with fines for those found to be flouting the rules.
“The incident rate across the area is now over 100 cases per 100,000,” Mr Hancock said.
“We know that a large number of these infections are taking place in indoor settings outside the home.
“And so at the request of the local councils, with whom we have been working closely, we will introduce legal restrictions on indoor mixing between households in any setting.
“We do not take these steps lightly.
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“But we must take them and take them now because we know that swift action is more likely to bring the virus under control.
“The quicker we can get this virus under control, the quicker we can restore the freedoms we all enjoy in the North East and across the country.”
The announcement comes as new local lockdowns, further restrictions and new fines came into force across parts of the UK.
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A minister suggested earlier that tighter social restrictions could be imposed if infections continue to rise.
People in England are now legally required to self-isolate if they test positive for COVID-19 or are told to do so by the test and trace service.
Those who do not comply risk being fined £1,000, increasing up to £10,000 for repeat offenders or serious breaches.
Anyone who tests positive and then knowingly provides false information about their close contacts will also be fined.
Health and social care minister Helen Whately told Sky News that “we don’t want to” bring in measures taking the UK back towards a second national lockdown but cautioned the government was keeping a “constant eye” on cases.
It follows a report in The Times that a “total social lockdown” could be enforced across much of northern Britain and London.
Measures reportedly being considered include more restrictions on people from different households meeting indoors, and shutting pubs and restaurants – initially for two weeks.
Schools, shops and offices would remain open, according to the newspaper.
It quoted a senior government source as saying the nation and Conservative MPs weren’t “ready” for such action but it “will have to come”.
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Ms Whately did not deny the plan is being considered.
“We have an opportunity – a choice – as a country to get this back under control again,” she told Kay Burley.
“This is our moment in time to make sure we’re doing social distancing and the rule of six. That’s how we control it.”
Three more council areas in South Wales went into local lockdown from 6pm on Monday – Neath Port Talbot, Torfaen and the Vale of Glamorgan.
Bans on households mixing came into force in Wigan, Stockport, Blackpool and Leeds on Saturday.
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Stricter rules are already in places across large parts of north west England, West Yorkshire, the North East and the Midlands, as well as in areas of west Scotland.
It means that an estimated 17.8 million people across the UK are now living under additional COVID-19 measures, on top of those already announced by the prime minister Boris Johnson.
A recent nationwide change has been the imposition of a 10pm curfew for pubs, bars and restaurants.
But ministers are coming under growing pressure to review the rule, amid criticism it is leading to people filling the streets en masse when venues close.
Labour is calling for a “rapid” review of the curfew.
Greater Manchester mayor Andy Burnham has told Sky News he fears the rule could be proving “counterproductive” in the fight against the virus.
“If this isn’t doing what it intended to do, then surely it’s right to adjust it or even remove it altogether,” he said.