Boris Johnson has said the government is considering tougher restrictions on travel from France to prevent coronavirus variants being brought into the UK.
The prime minister said putting France on the "red list" was "something that we will have to look at" due to concern over the effectiveness of vaccines against the new variants.
Speaking in front of senior MPs at the House of Commons Liaison Committee, he said "we have to look at the situation at the Channel", adding that "we can’t rule out tougher measures and we will put them in if necessary".
Labour MP Yvette Cooper, who chairs the committee, said France had between 2 and 3,000 cases of variants and asked why it was not on the "red list" of countries.
Mr Johnson responded: "We will take a decision, no matter how tough, to interrupt that trade, to interrupt those flows, if we think that it is necessary to protect public health and to stop new variants coming in.
"It may be that we have to do that very soon."
The PM said a balance had to be struck between the need to protect public health and any major disruption that would be caused to the flow of goods, including food and medicine.
Disruption to cross-Channel movement could see a repeat of the scenes around Christmas in which thousands of lorries were caught in a gridlock on the way to the Port of Dover.
This delay was also caused by concerns about the spread of variants of the coronavirus, although at that time it was France which wanted to stop potential contamination from reaching its shores.
In the end military personnel were drafted in to help get drivers tested and clear the logjam of vehicles.
The situation at that point was exacerbated by the looming end of the Brexit transition period.
It comes as Europe faces the prospect of a third wave of the coronavirus.
During today’s committee hearing, Mr Johnson was asked by Ms Cooper why hauliers are not currently being tested.
The prime minister replied: "Tougher measures would have very serious disruption on those trade flows and that has to be balanced against the current ambiguity about the effectiveness of the vaccines on the variants."
Sarah Laouadi, European policy manager at industry body Logistics UK, has said that drivers are "low-risk" and that testing must be "proportionate".
She said: "It is vitally important to protect the UK’s highly interconnected supply chain from the threat of new COVID-19 variants and rapid testing of drivers on arrival in the UK will provide additional confidence for those whose businesses they supply.
"However, it is worth remembering that drivers are, by the nature of their jobs and thanks to contactless delivery procedures, a very low-risk category – as has been borne out by the testing carried out on drivers since the start of the pandemic – and any testing regime must be proportionate."