An EU deadline for Britain to grant licences to dozens of French fishing boats is set to expire today, with Paris threatening legal action unless a last-minute compromise can be found.

France says that 104 of its boats still lack licences to operate in British and Channel Island waters that should have been granted under a Brexit deal Britain signed with the European Union in December last year.

Britain denies discriminating against French boats and says many of the applicant vessels are unable to provide the paperwork required to qualify for a licence.

France's Europe Minister Clement Beaune held out the possibility of Britain granting "a few dozen more as a gesture of goodwill," which would mean talks could continue.

"If they stick to their guns, then we will ask the European Commission to begin a legal complaint," he told Franceinfo radio on Friday.

He also said Britain tried to isolate France in the dispute, but the EU stood united.

"Boris Johnson told himself he could isolate the French. We have re-mobilised (the Euopeans) so that the deal is respected," Mr Beaune added.

British Environment Secretary George Eustice is to hold talks with EU Environment Commissioner Virginijus Sinkevicius today.

In Brussels, an EU spokeswoman said talks with Britain were underway and the goal is still to reach a deal.

"Where we are is that on both sides, on the European Commission and UK, we have agreed that we have this mutual commitment to end these discussions for the successful outcome today," Vivian Loonela said.

France and Britain have clashed repeatedly this year over fishing as well as migrants crossing the Channel, post-Brexit trade arrangements, and the sale of submarines to Australia.

London briefly deployed two navy gunboats in May when dozens of French trawlers massed in front of the island of Jersey to protest the licensing problems, prompting France to send two coastal patrol vessels.

French fishermen held another brief protest last month, blocking ferries and freight traffic through the Channel Tunnel.

Many analysts and diplomats see cross-Channel ties as being at their lowest ebb in at least two decades, and possibly more.

"The problem with the British government is that it does not do what it says," French President Emmanuel Macron told a news conference on Thursday, just weeks after he accused British Prime Minister Boris Johnson of having a "not serious" approach on tackling migration.

The British government has said it does not recognise today as a deadline to resolve the fishing row.

"We've never set a deadline. I recognise they themselves have set one but it's not one we're working to," Mr Johnson's spokesman told reporters on Thursday.

If France lodges a complaint with the European Commission, it could lead to the start of a formal infringement procedure against Britain.

The final step, if the two sides are unable to resolve their differences, could see the EU impose financial penalties or even tariffs on British goods if Britain is judged to be reneging on its commitments under the December 2020 Brexit deal.

The EU and Britain are also locked in a separate trade row over checks on products entering the British province of Northern Ireland after the UK government unilaterally postponed the introduction of checks.

Under the Brexit deal, European fishermen can continue to work in British waters as long as they can prove that they used to fish there.

France says small boats without GPS data are being penalised while Britain is also often refusing to issue licences to new boats that replaced older vessels in the French fishing fleet.

Britain denies the French claims.