"We consider that in any case it would be quite absurd."
It was the Kremlin's first reaction to the poisoning of two British citizens exposed to Novichok near Salisbury in England, where former Russian double agent Sergei Skripal and his daughter were poisoned in March.
Peskov added that "we of course very much regret the death of the British citizen."
Dawn Sturgess and Charlie Rowley were taken to hospital last weekend from a house in the town of Amesbury, around 12 kilometres (eight miles) from Salisbury, and were found to have been exposed to Novichok.
Police announced Sturgess's death yesterday.
Russia is "deeply concerned by the continuing appearance of these poisonous substances on British territory," which "present a danger not just for the British but for all Europeans," Peskov said.
Both the Skripals have now been released from hospital and are living in a secret location.
Putin has said that if a military-grade nerve agent had been used against them, the victims would have died.
Peskov today denied a suggestion by Russia's representative to the Organisation for the Prohibition of Chemical Weapons (OPCW) Alexander Shulgin that the incident appeared to be designed to damage preparations for a meeting between Putin and US President Donald Trump in Helsinki this month.
"It has nothing to do with the summit," Peskov said.
"It's more Britain's problem and the problem of how much Britain is interested in a real investigation.