Boris Johnson clashed with Labour leader Sir Keir Starmer in parliament on Wednesday.

Starmer said 21,000 people were entering the UK every day, with new border arrangements “weeks away”.

“They will only affect direct flights from some countries,” he said. He added the first pandemic showed only 0.1% of virus cases had come from China “where we had the first restrictions, whereas 62% came indirectly from France and Spain where there were no restrictions”.

He criticised the policy of only banning passengers on direct flights from red-list countries when there were numerous indirect options.

He asked why the government thought new variants "would only arrive by direct flights”.

Johnson reiterated the UK’s requirement for a negative Covid test 72 hours before flying and then 10 days’ quarantine. He said 75% of medicines came from Europe and 45% of food. “It is not practical to close off this country. What it is practical to do is have one of the toughest regimes in the world.”

Starmer said the biggest risk to the vaccine programme was the arrival of new variants.

“On that issue, the government’s own scientists (Sage) said two weeks ago only a complete, pre-emptive closure of borders and the mandatory quarantine of all visitors on arrival can get close to fully preventing new cases or new variants.

“Pretty clear – so why did the prime minister choose not to do the one thing that Sage said could prevent new variants coming to the UK?”

Johnson replied Sage “did not recommend a complete travel ban” and said the UK had one of the toughest regimes in the world.

He added: “It is illegal now to go on holiday in this country. It is illegal to travel from South Africa or all the countries on the current red list.

“We will be going forward with a plan to ensure people coming to this country from those red-list countries immediately have to go into government-mandated quarantine hospitality.”

Starmer said the prime minister “doesn’t seem to dispute” Sage’s view that only a complete closure or comprehensive quarantine will work, “he says it simply wasn’t a recommendation”.