It was the first time the Russian President has directly condemned Skripal, who spent weeks in hospital with his daughter Yulia after both were poisoned with Novichok in the city of Salisbury in March.
Dawn Sturgess, 44, who was later exposed to the same nerve agent, died in July.
Speaking at an energy forum in Moscow, Putin said: “I see that some of your colleagues are pushing the theory that Mr Skripal was almost some kind of human rights activist.
“He was simply a spy. A traitor to the motherland. There is such a concept – a traitor to the motherland. He was one of those.”
“He’s simply a scumbag, that’s all.”
Britain put the blame squarely on Russia for orchestrating the attack on the 66-year-old, but Moscow has denied any role in the incident.
Asked about sanctions on Russia triggered by the attack, Putin called the ex-spy “just a scumbag” who betrayed his country. He reiterated Russia’s claim that it has nothing to do with the poisoning.
Putin said the former agent was of no interest to the Kremlin since he was tried in Russia and exchanged in a spy swap in 2010.
However, as more information emerges about the two men behind the attack, further suspicions have been raised about the Kremlin’s possible role in the poisoning.
Last week, the two men identified by the UK government as being those behind the attack appeared on the Russian state-backed news channel RT and said they were merely “tourists” who visited Salisbury to see the city’s famous cathedral.
This short, off-season international jaunt just happened to coincide precisely with the poisoning of the Skripals. Their story quickly fell apart after it emerged no record of either men existed from before 2009 when passports under their names were issued.
One of the suspects was then identified as a colonel in Russian military intelligence (GRU), according to reports. An investigation by the website Bellingcat claimed Ruslan Boshirov is in fact 39-year-old Colonel Anatoliy Chepiga, a veteran GRU officer who has served in Chechnya and Ukraine.