Donald Trump yesterday hit Russia with new sanctions for election meddling and cyber-attacks as Washington vowed to punish Moscow’s “nefarious attacks”.

Nineteen people and five Russian organisations were targeted in what amounts to the most significant action against Moscow since President Trump took office.

The news came shortly after Western leaders backed Britain in blaming Russia for the nerve agent attack in Salisbury 10 days ago.

Mr Trump, with France's Emmanuel Macron and Germany's Angela Merkel, rallied round Theresa May after days of mixed messages, directly blaming Russia for the attack which left double agent Sergei Skripal and his daughter Yulia hospitalised.

Their joint statement represented a major boost for the Prime Minister and came 24 hours after she moved to expel 23 Russian diplomats and suspended high-level contact with Moscow in response to the Salisbury incident.

In the unprecedented joint message, Mr Macron, Mrs Merkel and Mr Trump said they agreed with Mrs May's assessment that there was "no plausible alternative explanation" for the attack.

The statement, issued by 10 Downing Street, said: “The United Kingdom briefed thoroughly its allies that it was highly likely that Russia was responsible for the attack.

“We share the UK assessment that there is no plausible alternative explanation, and note that Russia's failure to address the legitimate request by the UK government further underlines its responsibility.