Non-British vessels land an average of 58 per cent of the fish caught in UK waters each year

Theresa May is prepared to block access for European vessels to British fishing waters if talks with the EU over Brexit break down.

The prime minister is due to announce that Britain will pull out of the 1964 London convention, the agreement that gives EU nations access to fishing waters between six and twelve nautical miles from British shores.

Mrs May will say that she is serving a notice period of two years to exit the agreement, which would have allowed some European nations to fish in British waters even after Britain was no longer party to the EU common fisheries policy.

The goverment hopes that successful Brexit talks would include the right of some European countries to have access to British waters. But if