Travellers arriving in Britain from abroad will have to take two coronavirus tests during quarantine, the government is expected to confirm on Tuesday.
Health Secretary Matt Hancock is due to announce that people told to isolate at home will be required to get a test two and eight days into a mandatory 10-day quarantine period.
The new measures, which critics say come too late to curb the spread of the virus, are aimed at halting new variants.
But the health ministry said Britain's response had been informed by experts leading to "some of the toughest border regimes in the world".
"Enhancing our testing regime to cover all arrivals while they isolate will provide a further level of protection and enable us to better track any new cases which might be brought into the country, and give us even more opportunities to detect new variants," a spokesman said.
Environment Secretary George Eustice confirmed that announcements on the new quarantine regime would be made in parliament later on Tuesday.
"We have to be ever mindful of the risk of other variants entering the country," he told BBC radio.
Prime Minister Boris Johnson's government has been under pressure to tighten rules for international travellers, following criticism the regime was too lax.
New mandatory hotel quarantine rules for travellers returning from dozens of countries deemed "high risk" from Covid-19 are due to start from February 15.
The new rules will require all UK citizens and permanent residents returning from countries on a travel ban list to self-isolate in a government-approved facility for 10 days.
Other visitors from the 33 countries currently on the list, which includes all South American nations and South Africa, are currently barred from visiting Britain under virus lockdown rules.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)