Mr Skripal, 66, remains critically ill in Salisbury hospital after he was found slumped unconscious on a bench in Salisbury, following exposure to an unknown substance on Sunday.
The former Russian colonel in military intelligence and his 33-year-old daughter, Yulia Skripal, who had been visiting from Russia, were both found unconscious near a shopping centre in Wiltshire.
Mr Skripal was jailed in Russia for treason after passing state secrets to MI6 in 2006, before being given refuge in the UK as part of a spy swap eight years ago. Since then, he has continued to live a peaceful life in Salisbury.
Igor Sutyagin, 53, who was released in the same swap after being sentenced to 15 years in prison, now works as a research fellow at the Royal United Services Institute think tank.
The nuclear arms expert, who was also convicted of treason by a court in Moscow said today: “In theory, anyone can be behind the suspected poisoning in Salisbury, including North Korea.”
Mr Sutyagin, who has always maintained his innocence, also brought up the the assassination of Kim Jong-nam, Kim Jong-un’s estranged half-brother in Kuala Lumpur airport last February.
He said: “If to suspect this was not an accident, but an intentional poisoning – and some intelligence services are involved – then a clear rational analysis shows that the timing for such an action is most inappropriate.
“The flow of the negative information in the last three to four weeks was so dense that one should be a blithering idiot to add such a “log” to the fire. In theory, anyone can be behind this, including North Korea.
“They did a very similar thing with Kim Jong-un brother at Kuala Lumpur airport. It looks very similar.”
Mr Sutyagin told Radio Svoboda that when he met him, Mr Skripal seemed to be a nice, calm and normal man who did not seem the type to take drugs.
He and Mr Skripal flew together on a Russian plane to Vienna for the Cold War-style exchange deal, which involved Russian intelligence agent Anna Chapman and a few Russian sleeper agents.
They were among four convicts who were pardoned in a deal between the US and Russia that was said at the time to be one of the largest swaps since the Cold War.
But Mr Sutyagin warned against placing the blame on Russia for Mr Skripal’s suspected poisoning.
He told Associated Press: “There are lots of former security officers that deserted to the West. It is necessary to balance this information.”
Salisbury District Hospital declared a major incident the day after Mr Skripal and his daughter were admitted, and the fire service decontaminated the A&E department. But patients were told to attend appointments as normal unless told otherwise.
Wiltshire Police have yet to ascertain whether the pair, who are both in intensive care, have been victims of crime.
Temporary Assistant Chief Constable Craig Holden said: “The pair, who we believe are known to each other, did not have any visible injuries and were taken to Salisbury District Hospital.
“This has not been declared as a counter terrorism incident and we would urge people not to speculate. However, I must emphasise that we retain an open mind and we will continue to review this position.”
The suspected poisoning comes at a time of major tension between the UK and Russia.
Last year, a report from the Commons Foreign Affairs committee described the relations between the two countries as at “its most strained point since the end of the Cold War”.