People who see their neighbours breaching the "rule of six" should report them, the crime minister has said.
Kit Malthouse told the morning media round that residents should “absolutely” call the police if they see neighbours holding gatherings of seven or more next door.
The rule of six came into force overnight despite claims that it will keep families unfairly apart and wreck Christmas. Rule-breakers can be fined £100 , with penalties doubling for every further offence up to a maximum of £3,200.
The UK's reproduction, or R, number escalated to between one and 1.2 for the first time since March.
A further 3,330 positive cases were recorded in the UK on Sunday - the third consecutive day with more than 3,000 - with five more deaths reported.
Some Tory MPs want children under 12 to be excluded from the calculation of group sizes, while the former Supreme Court justice Lord Sumption today warned that the law will be “unenforceable”.
He said it would only work if a “Stasi-style” network of “snoopers and informers” was in place and denounced the legislation as “pointless, arbitrary and unnecessary”.
National Police Chiefs' Council (NPCC) chairman Martin Hewitt denied that enforcement of the rule of six relies on people "grassing up" their neighbours.
"It relies on all of us being responsible," he told BBC Breakfast.
Mr Malthouse defended the new regulations, saying that during lockdown there was a surge in reports coming through to police.
“If people are concerned, if they do think there’s been a contravention, then that option is open to them.”
He said that new guidance would be issued in the next “two or three days” by the college of policing to help officers decide when fines should be issued to those breaking the law.
Martin Hewitt, head of the National Police Chiefs' Council (NPCC), said police would respond to calls about law-breaking but would begin by explaining the law using a “four Es approach” — engage, explain, encourage, enforce — and that he anticipated most people would comply.
Hewitt said that only in circumstances where people refuse to comply will the police move to issue fines and take enforcement action.
Labour leader Sir Keir Starmer told LBC he backed the government's new rules, adding: "You can make the argument of why not five or why not six or seven - you have to go with a number backed by the science and they say six and I think we should abide by that rule."
Levels are still far lower than when they peaked in March, the virus is spreading far more slowly than pre-lockdown and the actions being taken now are aimed at preventing another lockdown.