The Federal Security Service (FSB), main successor to the Soviet-era KGB, said it had discovered that second secretary Albertus Gerhardus Janse van Rensburg was “carrying out intelligence ​and subversive activities that threaten the security of the Russian Federation”.

A spokesperson for Britain’s foreign ministry called ​the accusations “completely unacceptable”, accusing Moscow of harassing its diplomats by “pumping out malicious and completely ⁠baseless accusations”.

As it wages war in Ukraine, Moscow has accused Britain of pursuing espionage aimed at sowing discord within Russia ​at a level unseen since the depths of the Cold War.

Britain, which supports Ukraine with money and weapons, sees Russia as ​its biggest immediate threat and accuses Russian intelligence of mounting major cyberattacks, killings and sabotage campaigns across the Western world.

Russian state television aired videos that it said showed Janse van Rensburg meeting economic contacts in Moscow restaurants, and cross-country skiing beside what state TV said ​was a special defence ministry building.

Britain cast as Russia’s ‘public enemy number one’

State TV said Janse van Rensburg was ​the 16th British diplomat to be expelled from Moscow in two years. It was not possible to contact the diplomat.

The FSB said ‌he ⁠had attempted to “obtain sensitive information during informal meetings with Russian experts in the field of economics”.

“To avoid negative consequences, including criminal liability, the FSB of Russia recommends that compatriots refrain from holding meetings with British diplomats,” it added.

As the U.S. under Donald Trump seeks to reset ties with Moscow and broker peace between Russia and Ukraine, Britain ​has been granted the status ​of Russia’s public enemy number one.

On state television, “Perfidious Albion” is cast as scheming behind the scenes to undermine Russian interests around the world.

Western diplomats in Moscow say intrusive surveillance and harassment are frequent, and that ​a guide known as “Moscow Rules”, developed in Soviet times to guard against complacency, has been ​updated.

Russia has ⁠imposed Soviet-style restrictions on most British diplomats, requiring them to give notice of any plans to travel beyond a 120-km (75-mile) radius.

Diplomatic postings to Moscow are now considered among the most difficult in the world by Western countries. The U.S. ⁠State ​Department ranks Moscow alongside Freetown, Mogadishu, Damascus and Kabul in hardship ​terms.

Russia has long complained that its own diplomats are routinely harassed in major Western capitals, particularly in the United States.