More: Ex-double agent poisoned.
The Kremlin's Peskov called the allegation that Putin was involved "a shocking and unforgivable breach of the diplomatic rules of decent behavior", TASS news agency reported.
Russian Federation has repeatedly dismissed the UK's accusations as "unfounded" and warned it would retaliate over the expulsion of its diplomats.
U.K. Prime Minister Theresa May said it's "highly likely" the Kremlin is responsible for the March 4 attack against Skripal and his daughter.
"Our quarrel is with Putin's Kremlin and with his decision - and we think it is overwhelmingly likely that it was his decision - to direct the use of a nerve agent on the streets of the United Kingdom, on the streets of Europe, for the first time since the Second World War". It said it would not respond to Ms May's allegations until it was given samples of the poison used and such samples were handed to the global Organisation for the Prohibition of Chemical Weapons (OPCW).
Britain has blamed Russia for the poisoning and announced the expulsion of 23 Russian diplomats.
Mr Peskov said it had become "obvious that there is a lack of any clear proof [of Russian involvement]". In an unusual joint move Wednesday, the U.S., France and Germany also pointed the finger at Russian Federation.
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On Thursday, in a rare joint statement, the leaders of the United States, Germany and France joined May in accusing Russian Federation of being behind the attack.
The British government is right to want to bring the perpetrators to justice. In a statement late on Friday, May's office said the OPCW agreed to travel to Britain to collect a sample of the nerve agent.
After the first known offensive use of such a weapon on European soil since World War Two, Britain has pinned the blame on Moscow and given 23 Russians who it said were spies working under diplomatic cover at the London embassy a week to leave.
Meanwhile, Russia has opened its own criminal investigations into the murder of Nikolai Glushkov, who was found dead at his home in New Malden on Monday, and what it called the "murder" of Yulia Skripal, who remains in a critical condition in hospital after the nerve agent attack. Britain blamed Russian Federation for the attack.
And speaking out in Friday's Daily Telegraph newspaper, a member of Dt Sgt Bailey's family said he had been "very disappointed" with the response to the attack of the Leader of the Opposition, Jeremy Corbyn. They added that "Russia's failure to address the legitimate request by the United Kingdom government further underlines its responsibility".
He suggested that the possibility that the Russians had lost control of the unsafe nerve agent - which May floated Monday but has since discounted - could not be excluded. His daughter, who lives in Moscow, was visiting him when the pair fell ill and were later found unconscious on a bench in Salisbury.
The sanctions prompted a swift threat of retaliation from the Russian government.
Tensions with Moscow are growing before Russia's presidential election Sunday, after a nerve agent attack in Britain on a Russian ex-spy.