The maximum number of people who can legally gather in a house in England will be cut to try to stop another coronavirus spike, Sky News understands.
A government source said the figure will be reduced from 30 but the new number is still being ironed out as part of a "toughening up" approach.
It follows a sharp uptick in COVID-19 infections recently, with 2,948 reported on Monday - the highest number since 22 May.
Experts warn the comparison should be treated with caution because double the number of tests are being carried out now than then.
Under the government's current guidance, only groups from two different households should socialise indoors.
But the law says gatherings of 30 people are illegal and £100 fines can be issued for breaches, rising to £3,200 for subsequent offenders.
It comes amid complaints from some people that they cannot order a coronavirus test online, simply being told "this service is currently unavailable".
Sarah-Jane Marsh, director of testing at the Whitehall Test and Trace operation, said lab services are at a "pinch point" and offered her "heartfelt apologies".
Prof Jonathan Van-Tam, England's deputy chief medical, also intervened yesterday to warn cases are rising because people have "relaxed too much".
And fears are mounting ahead of the new university year beginning this autumn - with students preparing to travel across the country.
Robert Jenrick, the housing secretary, told Sky News students should "exercise a degree of caution... particularly when they go home and see their elderly relatives".
He added young people should use an "added degree of common sense this autumn".
Pupils have also been returning to school full-time, following a summer that saw Prime Minister Boris Johnson gradually ease lockdown restrictions, he said at a safe speed, in a bid to also revive the economy.