LONDON — Britain is to expel 23 Russian diplomats allegedly operating as undeclared intelligence officers after Moscow ignored a midnight deadline to explain how its nerve agent was used in the attempted assassination of a former double agent on U.K. soil.
The move — the largest such expulsion in three decades — “will fundamentally degrade Russian intelligence capabilities in the U.K. for years to come,” British Prime Minister Theresa May announced in Parliament Wednesday. “If they seek to rebuild them we will prevent them from doing so.”
The spy drama gripping Britain was reaching a climax with the prime minister detailing how she planned to retaliate against Moscow for its alleged role in the poisoning of Sergei Skripal and his daughter in Salisbury last week.
Britain earlier called for an emergency U.N. Security Council meeting in relation to the incident.
May has said that it was “highly likely” the regime of President Vladimir Putin was behind the attack and gave him until midnight Tuesday to provide an explanation.
Russia has denied any involvement and said it was not responding to May’s ultimatum until it received samples of the military-grade nerve agent investigators say was used in the attack.
“Everything that is done today by the British government is absolutely unacceptable and we consider this a provocation,” Russian Ambassador Alexander Yakovenko told Sky News outside the Foreign Office.
He added that Russia was “not ready to talk in the way of ultimatums.”
May also announced that she would authorize officials to detain those suspected of hostile state activity at the U.K. border — a power until now only permitted in relation to those suspected of terrorism.
She said Britain would also freeze Russian assets where there was evidence that they may be used to “threaten the life or property of U.K. nationals or residents,” and would suspend all planned high level bilateral contact between the two countries.
The prime minister also announced that no U.K. minister or member of the royal family would attend this Summer’s soccer world cup in Russia.
The measures surpass the U.K.’s response to the killing of Alexander Litvinenko, an ex-spy and Putin critic who died in 2006 after drinking green tea laced with radioactive polonium-210.
A public inquiry found the killing of Litvinenko had probably been approved by Putin, though Moscow denied responsibility for the killing. In response Britain expelled four Russian diplomats, imposed visa restrictions for officials and suspended security service cooperation.
Britain also briefed NATO allies on the nerve agent attack in Salisbury, and fellow alliance members called on Russia to address Britain’s questions, including “complete disclosure of the Novichok program.”
Meanwhile in Geneva, Britain told the U.N. Human Rights Council that the use of the military grade nerve agent in the attempted assassination breached international law and should serve as a warning to the international community.
“The council and the United Nations General Assembly have decried Russia’s violations of international law with alarming regularity. Its reckless behavior is an affront to all this body stands for,” British Ambassador Julian Braithwaite told the council.
The Chairman of the E.U. leaders Donald Tusk also condemned the attack and said he was ready to put the attempted assassination of the Russian double agent on the agenda of next week’s European Council meeting.
With the deadline ignored, May chaired a meeting of Britain’s National Security Council. Here, the prime minister, her top advisers and senior Cabinet ministers decided how to react to what May had earlier called an “unlawful use of force by the Russian State against the United Kingdom.”