A former KGB official has said that Vladimir Putin could order more killings because Britain is seen as a "soft touch".
Former General Oleg Kalugin has urged the government to strike back and expel the Russian ambassador to send an "adequate signal".
Kalugin, who was head of the KGB counterintelligence and is still a fugitive, has also said he would have been killed "a long time ago" if he lived in the United Kingdom, reports the Mirror.
The news comes after Russia asked Britain for help in identifying the two killers that the police believe carried out the Novichok poisoning in Salisbury in March.
Former KGB officer Oleg Kalugin, photographed in 1990, said Vladimir Putin could order more killings because Britain is seen as a "soft touch"
The couple, who are believed to have been using aliases, were named as Alexander Petrov and Ruslan Boshirov.
Mr. Kalugin said: "The Russians see Britain as a soft touch, I would not rule out more murders.
"Now that you have identified two assassins, I believe that Britain should, at least, expel the Russian ambassador, that would send an adequate signal.
Kalugin was Putin's chief in the KGB in Leningrad during the 1970s, and was one of three men present when the organization sanctioned the murder of the Bulgarian dissident Georgi Markov with a poisoned umbrella in London in 1978.
He believes that the Kremlin behaved differently when acting on American soil.
Mr. Kalugin said: "Just observe how the Russians and, before them, the Soviets have acted differently in the US Yes, they interfere in the elections, but never, as far as I know, they have even tried a Political murder in US territory.
He said: Now that you've identified two assassins, I think Britain should at least expel the Russian ambassador. That would send a proper signal & # 39;
"Of course, Britain has less means to make Putin feel threatened, but there has been a lack of strong action against it."
He also said that the government and security agencies & # 39; failed & # 39; in his work leaving Sergei Skripal, a former double agent, unprotected in Salisbury.
Skripal was a colonel of Russian military intelligence who was imprisoned for betraying agents of the British security service MI6. He moved to England in 2010 as part of an exchange of spies.
It is believed that the nervous agent Novichok was stained at the door of his house in the sleepy cathedral town of Wiltshire in March.
London blamed the Russian state for the attack, but Moscow strongly denied any participation.
The Skripals and Bailey recovered, but in June, a British couple fell ill with the same type of nerve agent in the nearby town of Amesbury.
Kalugin added that the British security services should have learned from the death of Alexander Litvinenko, who was poisoned with a radioactive substance in London in 2006.