Valentina Matviyenko, a Kremlin loyalist and speaker of the upper house of parliament, said Russia would retaliate.
“Without a doubt, Russia, as is diplomatic practice, will respond symmetrically and observe parity when it comes to the number of diplomats,” RIA news agency quoted her as saying on Wednesday.
What began as a row between London and Moscow after Britain accused Russia of using a nerve agent to poison Skripal and his daughter has now snowballed into an international chorus of rebuke for the Kremlin, with even some friendly governments ejecting Russian diplomats.
Adding to the list on Wednesday, Slovakia, Malta and Luxembourg each recalled their ambassador in Moscow for consultations, while Montenegro said it would expel a Russian diplomat. Slovakia and Montenegro, while both members of the US-led NATO alliance, are traditionally close to Russia.
The biggest demarche came from the United States, which on Monday said it was expelling 60 Russian diplomats.
Moscow has denied being behind the attack on the Skripals and says its adversaries are using it to whip up a campaign of “Russophobia.”
Skripal, 66, a double agent who was swapped in a spy exchange deal in 2010 and went to live in England, and Yulia Skripal, 33, were found unconscious on a public bench in a shopping center in Salisbury on March 4. They remain critically ill in hospital from the attack in which, British authorities say, a Soviet-era nerve toxin called Novichok was used.
Russia has already expelled 23 British diplomats, a tit-for-tat response to Britain’s expulsion of the same number of staff at the Russian embassy in London.
Adding to a drum beat of tough rhetoric coming from Moscow and London, the Russian foreign ministry raised the prospect British intelligence services had poisoned Skripal and his daughter.
“If convincing evidence to the contrary is not presented to the Russian side we will consider that we are dealing with an attempt on the lives of our citizens,” the ministry said in a statement.
In Australia, whose government said on Tuesday it would expel two diplomats, the Russian ambassador, Grigory Loginov, told reporters the world will enter into a “Cold War situation” if the West persists with its bias against Russia.