Police will patrol public spaces across London to enforce the tighter “rule of six” coronavirus restrictions.
Officers will also respond "swiftly" to reports of groups gathering in large numbers, according to the Metropolitan Police.
The force confirmed that fines of up to £100 would be issued “where necessary” when people fail to respond to warnings. Repeat offenders face a maximum penalty of £3,200.
The new regulations cut the size of permitted gatherings both indoors and outdoors from 30 to six from Monday, although there are a series of exemptions, including meetings for work or educational purposes, funerals or sporting activities.
Matt Twist, the deputy assistant commissioner who leads the Metropolitan Police’s response to the coronavirus, said: “Coronavirus has had an enormous impact on London and the life of Londoners and my thoughts are with all those who have battled the virus or who have lost loved ones.
"Our city has made huge sacrifices since the start of lockdown in March and officers across the Met have been working around the clock to keep London safe and support our heroic health colleagues.
“Throughout this period, the vast majority of Londoners have complied with the regulations. Today’s changes are an important step to reduce the spread of the virus and I would urge everyone to take them seriously and comply.
“We will be deploying resources across the capital to engage with groups of more than six to highlight the risks and regulations. Where necessary, officers will enforce the regulations. We will be working closely with the London boroughs and their enforcement teams, and doing all we can to persuade Londoners to take the threat seriously. Where people just won’t listen, and are putting everyone at risk, we absolutely will take enforcement action.
“It is very clear that we cannot control the spread of the virus through enforcement alone, and we need Londoners to work with us. Therefore, please continue to act responsibly – maintain social distancing, respect the new regulations and guidance, and help keep yourself, your friends and family safe.”
Senior police officers have questioned whether the new regulations can be enforced now that demand has increased since the lockdown was eased. Brian Booth, chair of the West Yorkshire Police Federation, said: “We just don’t have the resources, the world has woken up again and it’s busy.”
The Metropolitan Police said its officers would continue to use the “Four Es” model of policing adopted across the UK in relation to the coronavirus laws.
Officers will first engage, explain and encourage people to follow the regulations before deciding whether to enforce them with fines.
“Coronavirus remains a real and deadly threat and officers will be deployed in every borough to help keep people safe,” the force said.
“They will patrol public spaces and will also respond swiftly to incidents where groups gather in large numbers.”