Cooper met with Navalny’s widow Yulia Navalnaya at the conference this weekend.
“Russia saw Navalny as a threat,” Cooper said at the event.
“By using this form of poison the Russian state demonstrated the despicable tools it has at its disposal and the overwhelming fear it has of political opposition”, she added.
The UK has been joined by Sweden, France, the Netherlands and Germany in accusing Russia of the poisoning.
The Foreign Office said the UK has informed the Organisation on the Prohibition of Chemical Weapons of Russia’s alleged breach of the Chemical Weapons Convention.
Navalny – an anti-corruption campaigner and Russia’s most vociferous opposition leader – died suddenly in jail on 16 February 2024 at the age of 47.
In 2020 he was poisoned with a Novichok nerve agent. He underwent treatment in Germany, and was arrested at the airport upon his return to Russia.
