Russia's government is expelling 23 British diplomats and threatened further measures in retaliation in a growing diplomatic dispute over a nerve agent attack on a former spy in Britain.

The Russian Foreign Ministry said in a statement that it is also ordering the closure of the British Council in Russia and ending an agreement to reopen the British consulate in St Petersburg.

It ordered the diplomats to leave within a week.

Leader comment: This is Russia's weak spot

British ambassador to Russia, Laurie Bristow, leaves after a meeting at the Russian foreign ministry building in Moscow, Russia. (AP Photo/Pavel Golovkin)

The statement said the government could take further measures if Britain takes any more “unfriendly” moves toward Russia.

British Prime Minister Theresa May this week expelled 23 Russian diplomats and severed high-level contacts over the poisoning of ex-spy Sergei Skripal and his daughter Yulia.

They remain in critical condition in hospital.

Moscow and London have both ordered diplomats to be expelled in the deepening dispute.

Vladimir Dzhabarov, deputy chairman of the foreign affairs committee in the upper house of the Russian parliament, spoke on Saturday after Russia ordered 23 British diplomats to leave the country and that the British Council in Russia to be closed.

Britain this week ordered 23 Russian diplomats to leave the country, saying that Russia was not co-operating in the case of Sergei Skripal and his daughter, both found poisoned by a nerve agent that British officials say was developed in Russia.

“It is possible that (Britain) will continue to respond; we are ready for this. But London must understand that this will not do anything, it is useless to talk with Russia with such methods,” Mr Dzhabarov was quoted as saying by the state news agency RIA Novosti.

Russia expels 23 British diplomats as stand-off intensifies