May announced the moves on Wednesday after her government found Russia "culpable" of the nerve agent poisoning of former spy Sergei Skripal and his daughter Yulia in Britain.
Britain's foreign ministry and the Russian embassy in London have been doing battle on social media over the death of ex-double agent Sergei Skripal.
Moscow has slammed the accusations that it was behind the attempted murder of a double agent, defying the midnight Tuesday ultimatum set by Britain.
On Wednesday, British police confirmed for the first time that a nerve agent was used and that their probe was now an attempted murder investigation.
Sergei Skripal and his 33-year-old daughter Yulia were found unconscious on a bench in the southwest England city of Salisbury on Sunday.
Sergei Skripal was found unconscious with his daughter Yulia in the southwestern English city of Salisbury on Sunday.