A former Soviet scientist who helped create the nerve agent Britain says was used to poison ex-spy Sergei Skripal and his daughter says it is hard to believe Russia was behind the attack because the Skripals did not die immediately, saying Britain could have been behind the attack.
Professor Leonid Rink told the RIA news agency that the attack did not look like Moscow's work because Sergei and Yulia Skripal had not died immediately.
The Skripals remain alive but in critical condition more than three weeks after they were found unconscious in the English cathedral town of Salisbury.
Rink said the British could have been behind the attack.
"It's hard to believe that the Russians were involved, given that all of those caught up in the incident are still alive," he said. "Such outrageous incompetence by the alleged (Russian) spies would have simply been laughable and unacceptable."
Moscow has denied any involvement in the Skripals' case or that the Soviet Union or its successor state Russia developed Novichok at all.
Inspectors from the world's chemical weapons watchdog have begun examining the poison used in the attack which London blames on Moscow.
Rink told RIA it would have been absurd for Russian spies to have used Novichok to try to kill the Skripals because of its obviously Russian origin and Russian name.
"There are lots of more suitable substances," he said. "To fire the equivalent of a powerful rocket at someone who is not a threat and to miss would be the height of idiocy."
He dismissed British media reports that Yulia Skripal could have unwittingly carried Novichok from Moscow as "utter nonsense," saying Novichok would not have survived the journey.