Last Saturday a boat of migrants that had been zig-zagging between UK and French waters had been intervened by the Border Force cutter Valiant.
The migrants were taken to the UK even though they were not in trouble but had been travelling at a “slow” pace.
In a recording of a maritime radio conversation obtained by the Daily Mail, officers could be heard discussing the “legality” of the operation.
The conversation between British and French officers started at 12.23pm British time last Saturday.
The Mail reports a British officer with a northern accent could be heard proposing the unauthorised handover.
He then double-checks with his French counterparts that he has legal authorisation to carry out the manoeuvre.
He later asks: “Would you have a problem if we put our boarding boat into the water near the vessel, however, we will just escort it towards UK waters?”
At one point, the Athos officer says: “We give you legality to do this, no problem.”
It comes as the Home Offices faces growing pressures in a week when record numbers of migrants have crossed the Channel.
Nearly 600 migrants have been intercepted attempting to cross the English Channel in the past three days.
The Home Office has confirmed that the French authorities dealt with eight incidents involving 130 people on Friday with the UK dealing with four boats involving 83 people.
This follows 201 people being stopped by Border Force officers in eight incidents on Thursday.
France has blamed Brexit for the rise in people making the unsafe journey.
In May last year, Ms Patel asked her Paris counterpart to agree to more interception in French waters.
However, no deal was reached and instead, the UK gave France £28 million for extra beach patrols.
Since the start of this year, more than 4,300 have reached the UK, including 1,058 in the past seven days.