Sir Keir Starmer has said he is “determined” British border checks in Calais will continue.
A coalition of French mayors has called for an end to a deal that allows UK immigration checks to be carried out before crossing the English Channel.
The prime minister said he would be “taking this up with the French authorities”.
Sir Keir told BBC Radio Kent: “We need those checks to be carried out there.
“I’m taking this up with the French authorities because it’s a very important provision. I am concerned about that and determined to make sure that we get the checks where we need them.”
The prime minister also tackled the issue of small boat crossings.
With crossings close to exceeding 20,000 since Labour took power in the July elections, he said: “We need to break the gangs.
“Before I was a politician I was the chief prosecutor… and we took down gangs that were involved in terrorism, guns and drugs, and do not accept that the only gangs that can’t be broken are these gangs.”