PARIS, March 14 (Xinhua) -- France was awaiting final conclusions of British investigation into former Russian spy's poisoning before taking any retaliatory act against Moscow, a government spokesman said on Wednesday.

"We are waiting for the final conclusions and that the facts are fully proven before taking a position on such issue," the spokesman Benjamin Griveau told reporters after a weekly cabinet meeting.

Asked whether France was ready to retaliate as part of common European stance to support Britain, Grivaux said, "We do not do politics-fiction over serious and sensitive issues. Once the elements will be proven, decisions will be taken."

He also said, "What happened in Britain is a very serious act ... I recall that Britain is France's strategic and historical ally."

On March 4, former Russian intelligence officer Sergei Skripal and his daughter were found unconscious on a bench in a shopping center in the southern England city of Salisbury. They remain in a critical but stable condition.

British Prime Minister Theresa May on Wednesday announced that 23 Russian diplomats would be kicked out, the biggest such expulsion in three decades, after Russia failed to come out with concrete explanation on the attack as demanded by the British government.

Earlier this week, May blamed Moscow for the chemical attack which involved "military-grade nerve agent of a type developed by Russia".

On Tuesday, Russian Foreign Minister Sergei Lavrov said that Russia, while denying any involvement in the poisoning case, was ready to cooperate with Britain in the investigation of the incident in accordance with international law,

"Russia is innocent and Russia is ready to cooperate in accordance with the Chemical Weapons Convention if the United Kingdom condescends to honoring its international legal obligations related to the mentioned document," Lavrov told a press conference in Moscow.