MOSCOW, December 9. /TASS/. The case on the Salisbury poisoning of former Russian military intelligence officer Sergei Skripal and his daughter Yulia is nothing but a farce as the UK authorities are unwilling to cooperate in its investigation and literally destroy the evidence, chief of Russia’s Foreign Intelligence Service Sergei Naryshkin said on Sunday.

"Regrettably, the British side is unwilling to cooperate. Moreover, as we see it on our part, the British side keeps on destroying evidence, pets and other objects," he said in an interview with the Deistvuyushchiye Litsa (Political Actors) with Nailya Asker-zade on the Rossiya-1 television channel.

Truth, in his words, can be established only in joint investigation. "Only a joint professional investigation can probably help find out what really happened. Until now, we have been interpreting it as a farce, as a provocation," he said.

He recalled that the Russian side had offered assistance immediately after the incident and had been stressing its readiness to take part in the investigation of this incident.

Spokesman for the Russian Prosecutor General’s Office Alexander Kurennoy said earlier this week that no progress had been made on the situation around the Skripal case probe. The Prosecutor General’s Office issued numerous requests to the British side for any materials related to the case whereas no such requests came from London. "In this case this process is being politicized, and they do not contact us on this case. As for other issues, we continue cooperation as normal," Kurennoy said.

If the British version of the affair is to be believed former Russian military intelligence (GRU) Colonel Sergei Skripal, 66, who had been convicted in Russia of spying for Great Britain and later swapped for Russian intelligence officers, and his daughter Yulia, 33, suffered the effects of a nerve agent in the British city of Salisbury on March 4. Claiming that the substance used in the attack had been a Novichok-class nerve agent developed in the Soviet Union, London rushed to accuse Russia of being involved in the incident. Moscow rejected all of the United Kingdom’s accusations, saying that neither the Soviet Union nor Russia ever had any program aimed at developing such an agent.