Russian President Vladimir Putin on Wednesday branded former double agent Sergei Skripal a "traitor" and a "scumbag", saying Moscow knew he had cooperated with foreign intelligence after his release in a spy swap.
But he again denied any Russian involvement in the poisoning of Skripal, who Britain says was attacked with a Soviet-designed nerve agent by members of Russia's military intelligence in March.
"He is just a scumbag," a visibly angry Putin told an energy forum in Moscow.
"He is just a spy, a traitor to the homeland," Putin said in his toughest remarks about Skripal to date.
"He was caught, he was punished, he spent five years in prison, we let him go, he left and continued cooperating with, providing consultations to (foreign) security services."
The former Russian military intelligence colonel was found guilty of passing state secrets to Britain and sentenced to 13 years in prison in 2006. He was pardoned by then-president Dmitry Medvedev and released as part of a spy swap with the West in 2010.
Putin's statement that Skripal consulted foreign intelligence goes against previous statements by his spokesman that the ex-spy is "of zero value or zero importance" to Moscow.
It follows reports that Skripal in recent years helped expose several Russian agents in European countries.
The Russian president once again laughed off British charges that two members of Russia's GRU military intelligence service had sought to poison Skripal and his daughter Yulia with Novichok in the English city of Salisbury in March.
The Skripals survived but a British couple, Dawn Sturgess and Charlie Rowley, came into contact with the same nerve agent near Salisbury months later and Sturgess died.
Putin dismissed the crisis in relations with Britain that led to the largest expulsion of Russian diplomats from the West since the Cold War as a "row between security services".
"As we know, spying, like prostitution, is one of the world's most important professions," Putin said, drawing applause from the audience. He apparently misspoke as the euphemism for prostitution is "oldest profession."
He again denied charges Russia was behind the poisoning, saying: "No one had to poison anyone there (in Britain)."
"Sometimes I look at what is happening around this case and am simply amazed," Putin said. "The sooner (the Skripal scandal) is over, the better."
British authorities have accused Putin of being ultimately responsible for the poisoning, allegations the Kremlin denounced as "unacceptable."
Putin said Britain should go through proper channels to cooperate with Russia on the case by sending information to the prosecutor general so that Moscow "can look at what really happened".
Last month, Putin called for the two men suspected by Britain of seeking to assassinate Skripal to appear on television, and he claimed that they were civilians.
In an eyebrow-raisinginterview with the Kremlin-funded RT channel, the two, who gave their names as Ruslan Boshirov and Alexander Petrov, said they went to Salisbury as tourists, prompting ridicule in Russia and abroad.
Bellingcat, the British-based investigative group, said last week that "Boshirov" is in fact Anatoly Chepiga, a GRU colonel decorated with Russia's top honour, the Hero of Russia, who has lived and worked under an assumed identity since 2010.
The report, produced together with Russian investigative journalists -- one of whom later said he has left the country out of fear of prosecution -- published an old passport photo of Chepiga, which resembles Ruslan Boshirov.
Moscow dismissed the report, saying "there is no proof" as physical likeness means nothing, and the Kremlin said it would no longer discuss the subject with journalists.
This week, several media outlets published a new photo of Anatoly Chepiga featured among portraits of honoured graduates of his military school in the Far East, which also clearly resembles Boshirov.