Russia's expulsion of 23 British diplomats “doesn't change the facts of the matter” of the poisoning of a former double agent in an English city, Prime Minister Theresa May said on Saturday, Telegraph reported.

Russia was “in flagrant breach of international law,” she told her Conservative Party's spring forum, adding that Britain “will consider our next steps in the coming days”.

"But Russia’s response doesn’t change the facts of the matter - the attempted assassination of two people on British soil, for which there is no alternative conclusion other than that the Russian State was culpable. 

Relations between London and Moscow have crashed to a post-Cold War low over the Salisbury attack, the first known offensive use of a nerve agent in Europe since World War Two.