A senior Ukrainian government interpreter who attended sensitive security talks with Theresa May inside Downing Street has been arrested for allegedly spying for the Kremlin.

Ukraine’s security service on Thursday said it had arrested Stanislav Yezhov and opened a treason investigation, five months after he accompanied the country’s Prime Minister on an official visit to London.

The interpreter for Ukrainian cabinet ministers had been recruited by a Russian intelligence agency and had been electronically passing them secrets, authorities in Kiev alleged.

Mr Yezhov was seen in photographs interpreting for Volodymyr Groysman at a meeting with Mrs May at Downing Street in July, as well as a meeting with Joe Biden, then US vice president, in 2016.

Mr Groysman said in a Facebook post the spy had “long been working in the interests of a hostile government”, but it was not clear if he was already thought to be spying at the time of the London visit.