In addition to expelling 23 diplomats that British Prime Minister Theresa May said were spies, she said on May 14 that Britain would suspend all planned high-level bilateral contacts with Russia, revoking an invitation for Russian Foreign Minister Sergei Lavrov to visit, and that British ministers and the royal family would not attend the soccer World Cup in Russia this summer.
The Prime Minister also thanked the United States of America, NATO, and the European Union for their assistance and support in the aftermath of the attack.
The ex-spy, his daughter and a British policeman are still in serious conditions in hospital following the 4 March attack which saw a military grade Novichok nerve agent released in the Salisbury.
Russian Federation today declared 23 British diplomats personas non grata and suspended the opening of a consulate of the United Kingdom in Saint Petersburg and the activities of the British Council in this country, as punitive measures against London.
She warned that Britain "will never tolerate a threat to the life of British citizens and others on British soil from the Russian government".
Earlier this week the United Kingdom expelled 23 Russian diplomats after Moscow failed to respond to a deadline set by Theresa May.
The Russian Foreign Ministry summoned the British ambassador, Laurie Bristow, to a meeting on Saturday morning in central Moscow at its Stalin-era headquarters during which he was informed of the retaliatory measures.
Britain's top diplomat is pointing the finger directly at Russian President Vladimir Putin.
This diplomatic crisis has plunged Russia-U.K. relations to the lowest they've been since the Cold War. A British public inquiry found Putin had "probably" ordered that assassination.
Meanwhile new tensions have surfaced over the death this week of a London-based Russian businessman, Nikolai Glushkov. "There is to be no Russophobia as a result of what is happening", Johnson said on Friday.
Glushkov was an associate of oligarch and Putin foe Boris Berezovsky, who was also found dead in 2013, apparently having hung himself, though a coroner recorded an open verdict. And naturally Johnson demonstrated his outrage at Russia's politics. Detectives are keeping an "open mind" about the death, police said.