Pressed on Monday whether the government was too slow to implement the hotel quarantine policy, he replied: “I don’t think so — we moved as fast as we could to get that going”.
He also stressed that a “massive effort” was under way to prevent the strain spreading further and said that Public Health England (PHE) “don’t think there is a threat to the wider public”.
“If you look at what we have done in the case of the South African variant, a massive effort when in there,” Mr Johnson said. “The same is going on now to contain any spread of the Brazilian variant.”
But the Labour leader, who has previously pushed for a blanket hotel quarantine policy for all arrivals in the UK, said the discovery of the new variant showed the government had not “secured our borders in the way we should have done”.
Sir Keir added: “It demonstrates the slowness of the Government to close off even the major routes, but also the unwillingness to confront the fact that the virus doesn’t travel by direct flights.
“We know from last summer that a lot of virus came in from countries where it didn’t originate in, but people were coming indirect, and that’s the way people travel. I still think we haven’t secured our borders in the way we should have done, and the sooner that’s done the better.”
Last month, ministers introduced a mandatory 11-day quarantine in government designated facilities for travellers from 33 countries, including Brazil, which have been placed on the so-called “red list”.
In total, PHE has identified six UK cases of the concerning P1 variant first detected in the Brazilian city of Manaus – three in England and three in Scotland.
Three cases are Scottish residents who flew to Aberdeen from Brazil via Paris and London, who all tested positive while self-isolating. Other passengers who were on the same flight to Aberdeen are now being traced.
The other two cases in England are from the same household in South Gloucestershire after one person returned from Brazil on 10 February – just days before the government’s hotel quarantine rule came into force. Previous requirements forced individuals to self-isolate at home.
Labour MP Yvette Cooper, who chairs the Home Affairs Select Committee, earlier told BBC Radio 4’s Today programme: “We need to look at how these cases have arrived in the country in the first place in order to prevent others doing so.”
Mr Cooper said many travellers would have taken indirect flights from Brazil, and that the situation highlighted “gaps” in the system.
“These cases seem to have arrived a month after the Brazil variant was first identified and we were raising with the Government the need for stronger action,” she said.
Speaking to reporters on Monday, Mr Johnson also described the plan for easing restrictions — published last week — as a “one-way roadmap to freedom”, adding: “It is designedly cautious in order to be irreversible.”
He added: “That is what we are hoping to achieve. Some people say we should go faster, some people say we should be more hesitant. I think we are going at the right pace, education is the priority, getting all schools open on 8 March is something that we have set our hearts on for a long time and I am confident we will be ready.”
