Keir Starmer has demanded to know why Boris Johnson decided to overrule Priti Patel and not introduce strict border controls in March 2020.
The home secretary has claimed she was an “advocate” of closing the UK’s borders 10 months ago to try to stop the spread of coronavirus.
The prime minister has been under pressure to explain his decision not to introduce tough entry requirements sooner.
While some travel restrictions were in force during March, it was not until June that everyone arriving by plane was finally required to self-isolate.
On Monday, the government finally introduced rules requiring new arrivals to have proof of a negative Covid-19 test.
All travel corridors, allowing travellers from some countries to arrive without the need to quarantine, were also shut.
“Why did the prime minister overrule the home secretary?” Starmer asked Johnson during PMQs on Wednesday.
“What the home secretary said last night is not disputed. It’s that she was saying last March to the prime minister: ‘You need to shut the borders.’”
Johnson defended his decision and said the UK now had “one of the toughest border regimes in the world” and was doing “everything we can”.
In comments revealed by Guido Fawkes, Patel told a video meeting with the Conservative Friends of India group on Tuesday night: “On ‘should we have closed our borders earlier?’, the answer is yes – I was an advocate of closing them last March.”
The UK has been much slower in introducing strict incoming travel rules than many other countries, having chopped and changed various restrictions since the first case was identified almost one year ago.
New Zealand, which confirmed its first case of Covid on February 28, closed its borders to all non-residents on March 19. Residents returning home were required to self-isolate. On April 10 the rules were tightened with the isolation having to take place in government-run hotels.
Australia confirmed its first case on January 25 and its borders were closed to non-residents on March 20. From March 27 people returning home to Australia had to quarantine for two weeks, again in government-run hotels.
Professor John Edmunds, a member of the government’s Scientific Advisory Group for Emergencies (Sage), told Times Radio on Sunday ministers had taken a “rather lax” approach to travel.
It comes as Patrick Vallance, the chief scientific adviser, said scientists and the government had learned lessons over the last year .
But he told Sky News he had always advised ministers to “go earlier than you think you want to, go a bit harder than you think you want to, and go a bit broader than you think you want to, in terms of applying the restrictions.
“I’m afraid that’s a grim message but that is what the evidence says – you’ve got to go hard, early and broader if you’re going to get on top of this. Waiting and watching simply doesn’t work.”