Theresa May has warned the Kremlin that Britain will not be cowed by its decision to expel 23 British diplomats in an escalation of the dispute following the Salisbury attack.

Responding to President Putin's decision to escalate diplomatic tensions, Mrs May told a gathering of Conservative Party members that his antics would not distract from the fact that Russia was "in flagrant breach of international law."

Speaking at the Conservative Spring Forum in London, Mrs May said Russia's response, which includes shutting down the British Council, did not "change the facts of the matter".