Britain will expel 23 Russian spies as part of its “full and robust response” to the “barbaric” poisoning of former double agent Sergei Skripal and his daughter Yulia, Theresa May announced.

The Prime Minister said Russia was guilty of “an unlawful use of force” against the UK and it was time to “send a clear message” to Vladimir Putin.

She said: “Many of us looked at a post-Soviet Russia with hope. We wanted a better relationship and it is tragic that President Putin has chosen to act in this way.

“But we will not tolerate the threat to life of British people and others on British soil from the Russian Government. Nor will we tolerate such a flagrant breach of Russia’s international obligations.”

After a meeting of the National Security Council, which includes the heads of MI5, MI6, GCHQ and the Armed Forces, Mrs May announced the most wide-ranging sanctions against Russia since the Cold War.