LONDON, Nov 1 (Reuters) - Britain warned France on Monday to back down in a fish row within 48 hours or face legal action under the Brexit trade deal.

"The French have made completely unreasonable threats, including to the Channel Islands and to our fishing industry, and they need to withdraw those threats or else we will use the mechanisms of our trade agreement with the EU to take action," Foreign Secretary Liz Truss told Sky.

"The French have behaved unfairly. It's not within the terms of the trade deal. And if somebody behaves unfairly in a trade deal, you're entitled to take action against them and seek some compensatory measures. And that is what we will do if the French don't back down."