"There remains no alternative explanation about who was responsible - only Russian Federation has the means, motive and record".
It said the poison was of "high purity" but declined to identify it publicly, adding that "the name and structure of the identified toxic chemical are contained in the full classified report" issued to member states.
British Prime Minister Theresa May said on March 12 that Sergei Skripal and his daughter Yulia had been poisoned with a military-grade nerve agent from the Novichok group of poisons, developed by the former Soviet Union in the 1970s and '80s.
He also said Russia had a clear motive for attacking Skripal, a former Russian military intelligence officer who had been imprisoned in Russia for spying for Britain only to be set free in a spy swap in 2010.
According to the embassy's maycommentary, "the case against Russian Federation is based on three elements: the identification of the chemical agent, far-fetched speculations and conclusions regarding the "operational experience" and "motive", as well as unverifiable 'intelligence'". The attack shredded ties between Russian Federation and Britain and led to a crisis in relations between Moscow and the west including a huge wave of tit-for-tat diplomatic expulsions.
USA would not attack Syria over gas attack allegations: Syrian lawmaker
On Saturday, a chemical weapons attack in the rebel-held Syrian town of Douma was blamed on Syrian President Bashar Assad . Security Council, saying the Western powers had violated "the U.N. charter and the norms and principles of global law".
Despite initial fears that they would not survive, Yulia Skripal was released from hospital to an undisclosed location earlier this week, while her father is said to be improving rapidly. "The Kremlin must give answers", he said.
Russian Federation carried out secret tests on how to smear deadly nerve agents such as Novichok on door handles, Britain claimed today in a bombshell dossier of evidence against Moscow in the Salisbury poisoning case.
The letter from Mark Sedwill set out in clinical terms why Russian Federation had the means, the experience and the motive to carry out the attempted murders of Sergei Skripal and his daughter Yulia. But the agency did not try to say where the chemical was made, or by whom. She also said she would give interviews to the media in time, but asked the press to have patience while she recovers.
Russia's ambassador to the UK, Alexandr Yakovenko, said he had not read Sir Mark's letter but denied the claims in it.
The Russian embassy in London immediately raised doubts over the authenticity of the statement, claiming it "only strengthens suspicions that we are dealing with a forcible isolation of the Russian citizen".