Boris Johnson has been pranked by two Russians posing as the recently-appointed Armenian Prime Minster Nikol Pashinyan.

The Foreign Secretary spoke to impersonators Vladimir Kuznetsov and Alexei Stolyarov – known as Vovan and Lexus – for a full 18 minutes and discussed a number of sensitive topics including relations with Vladimir Putin and the Salisbury poisoning incident.

Johnson, after being handed the call by an aide, opened by congratulating Pashinyan “very sincerely” on being elected PM after leading a peaceful revolution in the country.

After offering “all the support and advice that we can”, Johnson added: ”Obviously we had hoped to have better relations with Russia than we currently do, I’m afraid that Russia seems unable to resist malign activity of one kind or another and we have to stand firm against them though I appreciate that your geography dictates a balancing act.”

The caller then went on to highlight a planned meeting between Pashinyan and Vladimir Putin in Sochi next week, saying “I hope he will not poison me with Novichok”.

Johnson responded by saying “nobody wants a new Cold War” but he was “we’re almost 100% sure” of Russia’s responsibility for the attempted murder of Yulia and Sergei Skripal, calling it “disruptive and bad for Russia”.

He added: “If I have a message to Putin, it’s that we don’t want a cold war but we do want to see an improvement in the way Russia behaves.”

Johnson also offered to share further evidence with Armenia “in due course”.

Vovan and Lexus regularly appear on Russian state media and have claimed a number of high profile victims in the past including the head of NATO and Elton John.

The Foreign Office said in a statement: “The Foreign Secretary realised it was a hoax, and ended the call. We checked it out and knew immediately it was a prank call.

“The use of chemical weapons in Salisbury and Syria, and recent events in Armenia are serious matters. These childish actions show the lack of seriousness of the caller and those behind him.”