Russia's Foreign Minister Sergei Lavrov is shifting the blame of the poisoning of double agent Sergei Skripal and his daughter after claiming that the nerve agent used on the Skripal's could be in the arsenal of the USA and UK.
The BBC's diplomatic correspondent James Landale said: "This is understood to strengthen the argument that this substance came from Russian Federation because it is more likely to have been created by a state actor with the capability to make the nerve agent".
Russian intelligence agents hacked Yulia Skripal's emails for at least five years before the Salisbury poisonings, a bombshell Government dossier has revealed.
The nerve agent used to poison a former Russian spy and his daughter in England has been confirmed as novichok, a series of highly-toxic substances developed in Russia and considered among the deadliest chemical weapons ever made. "Only Russia has the means, motive and record", he said.
"We have information indicating Russian intelligence service interest in the Skripals dating back at least as far as 2013, when email accounts belonging to Yulia Skripal were targeted by GRU cyber specialists", he said.
But Mr Sedwill's letter suggested the nerve agent used was most likely to have been made at a laboratory in Shikhany, near Volgograd, a branch of the State Institute for Organic Chemistry and Technology.
U.K. Prime Minister Theresa May rallied allies in the U.S., Europe, Australia and Canada to conduct coordinated expulsions of more than 150 Russian diplomats last month after she told parliament it was "highly likely" that Russia was responsible.
Moscow has strongly denied responsibility and says Britain is waging a defamation campaign against it.
Russian Federation had stopped its chemical programs in 1992 and eliminated all chemical weapons in 2017, he said.
Skripal and his daughter were found on March 4 unconscious in a bank of streets of British town of Salisbury.
"The codeword for the offensive chemical weapons programme (of which Novichoks were one part) was FOLIANT", he said.
St Thomas's, in the centre of Salisbury, will hold the service at 3 p.m. on Sunday, metres away from the site of the bench where the Skripals were found outside the Maltings shopping centre.
Russian Federation claimed to have destroyed its chemical weapons stockpiles but the letter says it has "produced and stockpiled" small quantities of Novichok "within the last decade".
In a statement issued on Wednesday via police Yulia said she was "seeking to come to terms with my prospects, while also recovering from this attack on me".
Zakharova added there were doubts that a recent statement by Yulia Skripal was authentic.