Theresa May got tough with Vladimir Putin after her 24-hour deadline expired for answers over how a nerve agent was used in Salisbury, Wilts.
The spies have a week to pack their bags. Mrs May said their exit would “dismantle the Russian espionage network in the UK”.
Russia’s Foreign Ministry pledged tit-for-tat expulsions, saying: “Our response will not be long in coming.”
The warning came as lawmaker Konstantin Kosachev said the lack of evidence of his country’s involvement “would have Sherlock Holmes turning in his grave”.
Mrs May accused Moscow of “sarcasm, contempt and defiance”.
And she told the Commons the bid to kill Mr Skripal, 66, and daughter Yulia, 33, must “be met with a full and robust response”.
She said royals would not attend June’s World Cup in Russia — as some MPs said the England team shouldn’t go.
The PM also cancelled an invitation to Russia’s foreign minister Sergei Lavrov — and vowed to kick out corrupt oligarch pals of Putin.
She even hinted at a cyber attack saying we will “deploy tools across our National Security apparatus”.
But Russian opposition leader Alexei Navalny said Mrs May had not gone far enough, adding: “Twenty three diplomats will be expelled — 23 oligarchs and corrupt officials will keep enjoying life in London.”
The expulsion is the biggest in 30 years since the Cold War. No10 sources said it will be followed by a push for international sanctions.
Russia’s Foreign Ministry branded Mrs May’s moves “a crude provocation” and “categorically unacceptable”.
And a Moscow cabinet minister insisted it had destroyed chemical weapons.
UN Secretary-General Antonio Guterres said any use of nerve agents as a weapon was unacceptable.
And Nikki Haley, US ambassador to the UN, said: “We stand in absolute solidarity with Great Britain.”
She said more attacks could take place without action, adding it was a defining moment.
Ex-GCHQ boss Robert Hannigan said our cyber experts are capable of great damage but added: “I don’t think we should go there . . it would play to the Russian narrative.”