Russian oligarchs and their associates have registered donations of more than £820,000 to the Conservative Party since Theresa May became prime minister, The Sunday Times can reveal.

May promised to distance her party from Russian donors when she took office, with allies briefing that she would “sup with a long spoon” and the prime minister insisting there would not be a “business as usual” relationship with Moscow. However, the party has declared donations worth £826,100 from Russian-linked supporters since July 2016.

Last night May was under pressure to return the cash over the attempted nerve-agent murder of the Russian former spy Sergei Skripal and his daughter Yulia in Salisbury last Sunday.

Marina Litvinenko, the widow of the former Russian dissident Alexander, who was killed by