"The text has been composed in a special way so as to support official statements made by British authorities and at the same time to exclude every possibility of Yulia's contacts with the outer world - consuls, journalists and even relatives", the Russian Embassy said in a statement, adding that her statement "only strengthens suspicions that we are dealing with a forcible isolation of the Russian citizen".
He said it included investigating ways of delivering nerve agents by applying them to door handles.
The letter was made public a day after investigators at the Organization for the Prohibition of Chemical Weapons confirmed British findings that the Skripals were poisoned with a military-grade nerve agent.
Sir Mark also revealed the Skripals have been being spied on by Russian Federation for at least five years.
It said specialists at Russia's GRU military intelligence agency, also accused of hacking Democratic emails released during the 2016 US election, targeted the email of Yulia Skripal at least as far back as 2013.
Russian Federation denies the British claims about Novichok, saying that it completed the destruction of all its Soviet-era chemical weapons arsenals past year under global oversight.
In a letter to the North Atlantic Treaty Organisation secretary general, Jens Stoltenberg, UK national security adviser Mark Sedwill says there is "no plausible alternative explanation" for the attack in Salisbury on March 4 that left the Skripals hospitalized.
"It is highly likely that the Russian intelligence services view at least some of its defectors as legitimate targets for assassination", he said.
'The Russian state has previously produced Novichoks and would still be capable of doing so'.More news: Jaguar Land Rover to cut 1000 jobs after 'slump due to Brexit'
More news: Tonya Harding, Kareem Abdul-Jabbar among 'Dancing With the Stars: Athletes' cast
More news: Minecraft Has Xbox Achievements on Nintendo Switch
"The codeword for the offensive chemical weapons programme (of which Novichoks were one part) was FOLIANT".
Richard Guthrie, an independent chemical-weapons expert, says an important detail in the investigation is that the toxic substance is of "high purity".
Although Russia signed the global Chemical Weapons Convention, it continued to "produce and stockpile small quantities of novichoks [nerve agents]", Sedwill claims in his letter.
Russian Federation has denied all involvement in the incident, which the United Kingdom blames on Moscow, and which has led to a spiraling diplomatic dispute between the two nations.
The correspondence was published following repeated calls from the Kremlin to provide evidence that Russian Federation was behind the attack on former spy Sergei Skripal and his daughter.
Alexander Yakovenko announced the Russian Embassy would be publishing its own report on the attack.
"We get the impression the British Government is deliberately pursuing the policy of destroying all possible evidence".
In a statement issued on her behalf by British police, Skripal said her father, Sergei, remained seriously ill and she was still suffering from the effects of nerve gas used against them in an attack that led to one of the biggest crises in Britain's relations with Moscow since the Cold War.
She said she had declined an offer of assistance from the Russian embassy "at the moment".