The British Embassy in Moscow must bring the number of its diplomats in Russia down to the number of Russian diplomats in the U.K., according to the Russian Foreign Ministry on Friday.
In a statement published on its official website, the Foreign Ministry said the reduction in numbers "must be done within a month".
"On March 30, British Envoy to Russia Laurie Bristow was summoned to the Russian Foreign Ministry.
"The envoy was informed that British side must within a month reduce its staff, to bring the total number of employees of British Embassy in Moscow and of the general consulates in Russia into compliance with the total number of Russian diplomats, administrative and technical staff in Great Britain," it said.
The envoy was also conveyed a protest against "provocative and unjustified actions of the British side, which inspired the groundless expulsion of Russian diplomats from a number of countries".
Meanwhile, envoys of other Western countries who also expelled Russian diplomats were arriving at the Russian Foreign Ministry to get their official notification about retaliatory measures from Moscow.
The U.S. and several western countries expelled 140 Russian diplomats in an orchestrated reaction this week following the poisoning of ex-Russian spy Sergei Skripal and his daughter Yulia in the U.K.
On Thursday, Foreign Minister Sergey Lavrov announced the expulsion of 60 American diplomats and the closure of the U.S. Consulate General in Saint Petersburg.
The foreign minister had also said Russia was convening an extraordinary meeting of the Organization for the Prohibition of Chemical Weapons (OPCW) on April 4 to discuss the Skripal poisoning case.
Skripal, 66, and Yulia, 33, were admitted to a hospital on March 4 after being found unconscious in the southern English city of Salisbury.
Skripal was granted refuge in the U.K. following a 2010 spy exchange between the U.S. and Russia. Before the exchange, he was serving 13 years in prison for leaking information to British intelligence.
