PRIME Minister Theresa May has today confirmed that the nerve agent used to poison Sergei and Yulia Skripal is of Russian origin, and that it was "highly likely" to have been a state-ordered attack. 

Addressing MPs just after 5pm, Mrs May said the substance was "clearly a militarly grade nerve agent of the type developed by Russia", before naming it as Novichok.

Mrs May said it was "highly likely that Russia was responsible" for the attack "based on the positive identification of this chemical agent by world-leading experts at the Defence Science and Technology Laboratory at Porton Down; our knowledge that Russia has previously produced this agent and would still be capable of doing so; Russia's record of conducting state-sponsored assassinations; and our assessment that Russia views some defectors as legitimate targets for assassinations".

Russia's ambassador in London has been summoned to the Foreign Office to explain whether the attack was planned by the Russian state.

She said: "Either this was a direct act by the Russian state against our country or the Russian government lost control of its potentially catastrophically damaging nerve agent and it got into the hands of others."

And she said the government "will not tolerate such a brazen attempt to murder innocent civilians on our soil". 

Mrs May added: "This was not just a crime against the Skripals, it was an indiscriminate and reckless act against the United Kingdom, putting the lives of innocent civilians at risk."

The prime minister said if the government does not receive "a satisfactory response" from the ambassador, "we will conclude that this action amounts to an unlawful use of force by the Russian state against the UK, and I will come back and set out the response".

And Foreign Secretary Boris Johnson told the Russian ambassador that Russia must "immediately provide full and complete disclosure" of its Novichok nerve gas programme to the Organisation for the Prohibition of Chemical Weapons and has until the end of tomorrow to respond, according to Sky sources.