Andrei Kelin's remarks were made during an interview for the BBC's HARDtalk programme and appear to suggest Moscow will not hesitate to take assertive action to protect its sovereignty. The Kremlin reacted in fury after the British destroyer HMS Defender sailed through waters south of the Crimea peninsula in June. The incident sparked a diplomatic row, with Russia accusing the UK of committing a "gross violation" of the UN Convention's sea laws.

       Mr Kelin told his BBC interviewer: "We did not say that we would open fire, as some parliamentarians may have said, but next time it will be much more difficult for them, because this is not the first time a British warship has done this."

       The diplomat added that he did not believe the British government's claims at the time that it was "just an innocent passage of a ship."

       HMS Defender was on its way from Odessa to Georgia when it was shadowed by more than 20 Russian fighters and two coastguard ships, as it passed by the Crimea.

       The peninsula was annexed by Russia in 2014, a move that has not been recognised internationally.

       Since the annexation, Moscow views the waters around Crimea as Russian territory, that is off-limits to foreign ships.

       The UK said that HMS Defender was passing through Ukrainian waters in a commonly used and internationally recognised transit route.

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       Moscow's Defence Ministry claimed that its patrol ship fired warning shots and that a jet dropped bombs into the path of the British destroyer.

       This account was rejected by the British Government, who issued a statement in a tweet, which said: "No warning shots have been fired at HMS Defender.

       "We believe the Russians were undertaking a gunnery exercise in the Black Sea and provided the maritime community with prior-warning of their activity.

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       "No shots were directed at HMS Defender and we do not recognise the claim that bombs were dropped in her path."

       Relations between Britain and Russia have deteriorated steadily ever since Vladimir Putin came to power in 2000.

       The UK has accused Moscow of being behind poison attacks on former KGB officer Alexander Litvinenko in 2006 and then former GRU officer Sergey Skripal and his daughter Yulia in 2018.