Millions of people in parts of northern England are now facing new lockdown restrictions, which ban separate households from meeting each other at home after a spike in Covid-19 cases.
The rules impact people in Greater Manchester, east Lancashire and parts of West Yorkshire.
The health secretary told the BBC the increase in transmission was due to people visiting friends and relatives.
Labour criticised the timing of the announcement – late on Thursday night.
Health Secretary Matt Hancock told BBC Breakfast the government had taken “targeted” action based on information gathered from contact tracing, which he said showed that “most of the transmission is happening between households visiting each other, and people visiting relatives and friends”.
The new lockdown rules, which came into force at midnight, mean people from different households will not be allowed to meet in homes or private gardens.
They also ban members of two different households from mixing in pubs and restaurants, although individual households will still be able to visit such hospitality venues.
The changes come as Muslim communities prepare to celebrate Eid this weekend, and nearly four weeks after restrictions were eased across England – allowing people to meet indoors for the first time since late March.
The same restrictions will apply in Leicester, where a local lockdown has been in place for the last month.
However, pubs, restaurants and other facilities will be allowed to reopen in the city from Monday, as some of the stricter measures are lifted.
The health secretary said that the latest restrictions was not an attempt to curtail Eid celebrations after Miqdaad Versi, from the Muslim Council of Britain, said the restrictions were likely to have a “large impact” on Muslim families celebrating Eid.
Asked on BBC Radio 4’s Today programme whether the measures were announced late on Thursday night to stop the celebrations from taking place, Mr Hancock said: “No, my heart goes out to the Muslim communities in these areas because I know how important the Eid celebrations are.”
He added that he was “grateful” to local Muslim leaders and imams across the country who have “been working so hard to find a way to have Covid-secure celebrations”.
Mayor of Greater Manchester Andy Burnham has backed the measures, which he said would be reviewed on a weekly basis.
However, Labour leader Sir Keir Starmer, while also welcoming the measures, condemned the government’s decision to announce the changes on Twitter just after 21:00 BST on Thursday as “a new low for the government’s communications during this crisis”.
The government published details of the new restrictions two hours after the health secretary tweeted the announcement, and then released further guidance on the changes on Friday morning.
Ministers have said police forces and councils will be given powers to enforce the new rules.__BBC