An escalating crisis with France Britain threatens to inspect fishing vessels and Johnson pledges to defend his country's interests

London on Friday threatened to tighten inspections of European fishing vessels in British waters, in response to measures announced by France, in the first escalation between the two sides since Britain left the European Union.

A British government spokesman said in a statement that London "intends to launch a dispute resolution mechanism provided for in the post-Brexit trade agreement", which would include "carrying out a thorough inspection of the EU's fishing activities in UK territorial waters".

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British Prime Minister Boris Johnson pledged - in a later statement - to defend his country's interests in the fishing crisis with France.

Johnson's spokesman said he was expected to meet the British Prime Minister and French President Emmanuel Macron on the sidelines of the G20 summit in Rome on Saturday and Sunday.

He added, without giving further details, that Johnson "will discuss a range of issues" and stressed that France remains a close and strong ally of Britain.

Paris and London accuse each other of violating the post-Brexit trade agreement - which was reached at the end of last year - regarding fishing licenses in British waters.

France said during the past days that it would impose sanctions on Britain if it did not allow more French ships to fish in its territorial waters, and detained a British fishing vessel, and threatened to tighten inspections and prevent British ships from docking in French ports.

Call the ambassador

London summoned the French ambassador, Catherine Colonna, on Friday afternoon, to inform her of her protest against the French threats.

In the same context, British Environment Minister George Eustice said, "This is a game that two people can play."

"It is clear that we always have the option to escalate the measures we take on French ships and board more of them if that is what they are doing with our ships," he told BBC television.

The escalation is part of a wider dispute over post-Brexit trade arrangements, which could disrupt trade across the Channel and undermine British-French relations if it gets out of hand.