Britain's Prime Minister Theresa May addresses the House of Commons on her government's reaction to the poisoning of former Russian intelligence officer Sergei Skripal and his daughter Yulia in Salisbury, in London, March 14, 2018. Parliament TV handout via REUTERS

LONDON (Reuters) - British Prime Minister Theresa May will speak with French President Emmanuel Macron on Thursday after France said it was too early for Paris to decide whether action should be taken following a nerve agent attack on a Russian ex-spy in Britain.

French government spokesman Benjamin Griveaux has said decisions would be made only once Russian involvement was proven.

Foreign Secretary Boris Johnson, who described the evidence of Russia’s involvement as “overwhelming”, told BBC radio that May and Macron would discuss the attack later on Thursday.

“They issued a joint statement yesterday condemning the attack on UK soil and the PM is speaking to President Macron again today,” he said.