Grandparents will now be allowed to look after children in areas that have a local lockdown, Matt Hancock has announced.
Millions of people across the UK are under restrictions that ban them from socialising with people outside of their own households.
But concerns had been raised this prevented parents from going to work as they needed to stay home to look after their young children.
Speaking in the Commons on Monday, Hancock said: “I have heard the concerns about the impact local action on childcare arrangements.
“For many, informal child care arrangements are a lifeline without which they could not do their job.
“Today I am able to announce a new exemption for looking after children under the age of 14 or vulnerable adults, where that is necessary for caring purposes. This covers both formal and informal arrangements.
The health secretary added: “It does not allow for playdates or parties, but it does mean a constant child-care relationship that is vital for someone get to work is allowed.”
Boris Johnson will tomorrow convene a meeting of the government’s emergency Cobra committee before making a statement in the Commons.
The prime minister is expected to announce new measures designed to halt the recent surge in coronavirus infections.
Patrick Vallance, the government’s chief scientific adviser, warned on Monday there could be 50,000 daily cases of Covid-19 in the UK by mid-October.
He said this could lead to 200 deaths a day by mid-November if the current rate of infection is not halted.
Chris Whitty, the chief medical officer, suggested curbs to social lives were needed to prevent the virus spiralling out of control,
He said there was a need to “break unnecessary links” between households and a need to “change course”.
The two top scientists took part in a televised press briefing without a minister.