Boris Johnson is considering tougher restrictions on travel from France to prevent the importation of coronavirus variants despite the risks to cross-Channel trade.
The Prime Minister said a balance had to be struck between the need to protect public health and the major disruption that would be caused to the flow of goods including food and medicine.
His comments to MPs came amid concerns about the spread of the South African and Brazilian variants of coronavirus.
Home Affairs Committee chairwoman Yvette Cooper said France had 2-3,000 cases of the variants and questioned why it was not on the “red list” of countries from which travel is effectively banned.
She acknowledged that the need for trade would mean quarantine was not appropriate for hauliers but questioned why they were not being tested for coronavirus.
Mr Johnson said putting France on the “red list” was “something that we will have to look at” due to concerns about the effectiveness of the vaccines against new variants.
Appearing before the Liaison Committee of senior MPs he said “we have to look at the situation at the Channel” and “we can’t rule out tougher measures and we will put them in if necessary”.
When France required the testing of hauliers crossing the Channel in December it led to thousands of lorries being stranded in Kent while the arrangements were put in place.
Mr Johnson said: “There is a balance to be struck and what we don’t know is the exact state of the efficacy of the vaccines against the new variants and we have to balance that against the very serious disruption that is entailed by curtailing cross-Channel trade.
“This country depends very largely for the food in our shops, for the medicines that we need on that trade flowing smoothly.
“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.”
His comments followed reports that Mr Johnson is under pressure from England’s chief medical officer Chris Whitty and his deputy Jonathan Van-Tam to implement tougher border controls.
Logistics UK said any testing regime of hauliers arriving in the UK from France must be “proportionate”.
Sarah Laouadi, European policy manager at the trade body, 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.”
Mr Johnson’s comments came as the European Commission announced tougher rules for the export of vaccines as its dispute with AstraZeneca continued.
The move could result in supplies of vaccines from the bloc to the UK being blocked unless shipments of AstraZeneca jabs also travel from Britain to the continent.
Mr Johnson warned a “blockade” on vaccines could cause long-term damage but said he continued to work with his European partners.
A joint statement from Mr Johnson’s Government and the commission said they were “discussing what more we can do to ensure a reciprocally beneficial relationship” and create a “win-win situation” to expand vaccine supply on both sides of the Channel.
The UK is currently far ahead of the UK in the proportion of adults given a first dose of vaccine.
Government data up to March 23 shows 28,653,523 people have received a first dose – a rise of 325,650 on the previous day.
A further 98 people had died within 28 days of testing positive for Covid-19 as of Wednesday, bringing the total by that measure to 126,382.
As of 9am on Wednesday, there had been a further 5,605 lab-confirmed cases in the UK, bringing the total to 4,312,908.
The Government’s target is to offer all adults a jab by the end of July but work is being carried out on whether to extend the programme to cover children.
While children are unlikely to fall ill with Covid-19, they do play a role in transmitting the virus.
The University of Oxford is currently carrying out a clinical trial on children to test the safety and efficacy of its vaccine in younger age groups, with initial results expected in the summer.
Responding to reports that children could be vaccinated from August, Adam Finn, a member of the Joint Committee on Vaccination and Immunisation (JCVI), told ITV’s Good Morning Britain: “As far as I know, there has been no decision made to immunise children starting in August, or indeed any decision been taken to immunise children at all at this point.
“But it’s certainly something that we might need to do.”
Currently, only children at very high risk of severe infection are offered a jab.
A spokesman for the Department of Health said: ”While clinical trials are under way to test the efficacy and safety of Covid-19 vaccines in children and young adults, these trials have not concluded yet.
“We will be guided by the advice of our experts on these issues, including the independent JCVI.”