The French government warned it was "ready to use retaliation measures," after the UK set new rules governing access for fishing boats near the Channel Islands.
In the latest sign of post-Brexit fishing tensions, French maritime minister Annick Girardin told lawmakers: "I am sorry it has come to this ... but we will do so [retaliate] if we have to."
The minister also hinted that underwater cables that supply the islands with electricity from mainland France may be the target for the "retaliation," according to AFP.
French fishing vessels say they are being prevented from operating in British waters because of difficulty obtaining licenses.
On Friday, the UK authorized 41 ships equipped with Vessel Monitoring System technology to fish in waters off Jersey, an island in the Channel, with is a self-governing British Crown Dependency.
But there were also new demands that "were not arranged or discussed [with France], and which we were not notified about," the French fisheries ministry said.
The measures effectively create new zoning rules for the waters near Jersey "where the ships can go and cannot go," as well as stipulating the number of days the fishermen can spend at sea and what machinery they use, the ministry added.
"This is absolutely unacceptable," Girardin said. "If we accept this for Jersey, it would imperil our access everywhere."
Long-running tensions between British and French sailors were supposed to be solved by the Brexit Trade and Cooperation Agreement, but it has left many in the UK feeling let down.
"Disillusionment, betrayal and fury," were some of the words used after the deal's fishing agreement was revealed.
It is the second disagreement over UK fishing rights in a week, after the country's government failed to reach an agreement with Norway. It means no UK boats can fish in Norwegian waters in 2021.