Officials in the countries are working on proposals that would allow the guards to board ferries in French ports and stay onboard to the UK, the Times reported.

British maritime officials have asked France to provide an appraisal of the security situation and outline how the plain-clothed officers would operate.

A Whitehall source told the newspaper: “The French want to do this. We have asked how it will work.”

This week, Brittany Ferries carried out an exercise with guards on the Mont St Michel ferry, from Portsmouth to Caen, as part of moves to integrate the military personnel into the security network.

A permanent unit allowing patrols to be flown on to ferries in French and international waters has been operational since the beginning of the month.

According to the Times, France wants to expand the operation to enable guards to permanently be on French-flagged vessels as they travel across the Channel and into British ports.