In a statement issued after the meeting with Bristow, the Foreign Ministry said that 23 British diplomatic staff were "declared persona non grata and to be expelled within a week."
The statement also said that:
This move was a response to Britain's "provocative actions" and "baseless accusations" over the attack.
Permission was being withdrawn for Britain to open a general consulate in St. Petersburg.
"If further unfriendly actions are taken towards Russia, the Russian side retains the right to take other answering measures."
'An attack on international values'
Following Russia's announcement, Bristow called the nerve-agent poisoning "an attack not only on the United Kingdom, but upon the international rule-based system on which all countries, including Russia, depend for their safety and security."
He told reporters the attack was carried out "using a chemical weapon developed in Russia and not declared by Russia at the Organization for the Prohibition of Chemical Weapons, as Russia was and is obliged to do under the Chemical Weapons Convention."
Britain's Foreign Ministry said that it had anticipated Russia's response and that the National Security Council would meet early next week to consider what steps to take next.
"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," it said in a statement.