The international chemical weapons watchdog has handed its report on the Salisbury nerve agent attack to the UK Government after completing its investigation, the Foreign Office has disclosed.

A spokesman said they had asked the Office for the Prohibition of Chemical Weapons (OPCW) to release an executive summary of its findings at midday on Thursday.

"In line with established practice they have now shared a final copy of the report with us, as the requesting state," the spokesman said.

"We have asked them to distribute this version to all state parties to the Chemical Weapons Convention, including Russia, tomorrow and to publish the executive summary for all to see at 12pm BST.

"This transparent and open approach, which we have pursued from the outset, is in sharp contrast to the Russian state's ongoing tactics of obfuscation and distraction."

The move comes amid repeated attempts by the Kremlin to challenge Britain's claims that it was responsible for the poisoning of former double agent Sergei Skripal and his daughter, Yulia, in the Wiltshire city last month.

Theresa May has said that UK military experts at Porton Down found that they were poisoned by Novichok, a nerve agent developed by Russia, and that the only plausible explanation was that the Russian state was responsible.

Despite the denials from Moscow, Britain has received strong diplomatic backing from western allies for its stance, with more than 20 countries expelling in excess of 150 Russian diplomats in protest at the Russian actions.

Last week, a Russian call for a new joint investigation was voted down by 15 votes to six at a meeting of the OPCW executive council in The Hague.