Updated at 1.20pm

RUSSIA’S EXPULSION OF 23 British diplomats “doesn’t change the facts of the matter” of the poisoning of a former double agent in an English city, Prime Minister Theresa May has said.

Russia was “in flagrant breach of international law,” she told her Conservative Party’s spring forum, adding that Britain “will consider our next steps in the coming days”.

“Russia’s response doesn’t change the facts of the matter – the attempted assassination of two people on British soil, for which there is no alternative conclusion other than that the Russian State was culpable,” she said.

May blames Russia for the nerve agent attack on former spy Sergei Skripal and his daughter Yulia in the English city of Salisbury on 4 March, which has left them both fighting for their lives.

She warned that Britain “will never tolerate a threat to the life of British citizens and others on British soil from the Russian government”.

But she said Britain had “no disagreement with the Russian people”.

Earlier this week, Britain announced the expulsion of 23 Russian diplomats and suspension of high-level contacts over the poisoning.

Moscow responded today by expelling 23 British diplomats from Moscow in a tit-for-tat measure.

“Twenty three diplomatic staff at the British embassy in Moscow are declared persona non grata and to be expelled within a week,” the foreign ministry said in a statement after summoning the British ambassador Laurie Bristow.

British ambassador Laurie Bristow arrives at the Russian Foreign Ministry headquarters in Moscow. AFP / Getty Images AFP / Getty Images / Getty Images

It would also halt activities of the British Council across the country, it said.

“Due to the unregulated status of the British Council in Russia, its activity is halted,” the foreign ministry said in a statement referring to Britain’s international organisation for cultural relations and educational opportunities.

It also said it would halt the activities of the British Council, the country’s international organisation for cultural relations, in Russia.

“We are profoundly disappointed at this development,” the British Council said in a statement.

It is our view that when political or diplomatic relations become difficult, cultural relations and educational opportunities are vital to maintain on-going dialogue between people and institutions.

Britain said it had “anticipated a response of this kind” and that its National Security Council would meet early next week to consider its “next steps”.

Relations between the two countries have deteriorated rapidly in the 10 days since ex-spy Sergei Skripal and his daughter Yulia were attacked with a nerve agent in Salisbury, south-west England.

May said earlier this week that Russia was “culpable” for the attack, either directly or because Moscow had “lost control” of the nerve agent.

On Wednesday Britain said it would “suspend all high-level bilateral contact” with Russia, and expel 23 Russian diplomats, suspected of being spies, out of the UK.

No British royals or ministers will attend the World Cup in Russia, May told the House of Commons.

The US, France and Germany have all supported the UK’s decision to take action against the first use of a nerve agent in Europe since the Second World War.

- with reporting from Gráinne Ní Aodha

Read: Britain, France, the US, and Germany united in ‘abhorrence’ over first nerve agent attack in Europe since WWII

Read: Britain to expel 23 Russian diplomats after former double agent poisoned