The broadcaster, which is funded by the Kremlin, provides English language news on its satellite channel across Europe.
Tweeting in Russian, its chief executive Margarita Simonyan said: “They”ve closed our accounts in Britain. All our accounts. “The decision is not subject to review.” Praise be to freedom of speech!”
The move to freeze its accounts comes as EU leaders prepare to hold talks over how to stop Vladimir Putin “meddling” in European politics by spreading disinformation and propaganda.
Brussels believes that the Russian strongman is deliberately funding far-right and eurosceptic movements across the continent in a bid to undermine the unity of the bloc.
Senior diplomats have revealed that “several” countries have stepped up monitoring of Russian propaganda outlets in recent weeks amid accusations that Mr Putin is also trying to influence the outcome of the US Presidential election.
Allies of Hillary Clinton have accused Russia of deliberately leaking hacked materials, including emails linked to her campaign, in a bid to discredit her and boost Donald Trump.
The Kremlin has previously been linked to the far-right Front National, in France, after a Russian bank gave Marine Le Pen”s party a nine million euro loan in 2014.
Diplomats were also on edge during this spring”s Dutch referendum on free movement for Ukrainian citizens amid concerns Mr Putin could attempt to sway the result through propaganda.
And Fredrik Wesslau, from the European Council on Foreign Relations think-tank, said: “Russia is obviously not the mastermind behind the rise of populism in Europe but it”s clear that Russia is embracing it and, in some cases, actively supporting populist movements and far-right parties with pro-Russia sympathies.
“Moscow sees these populist parties as useful allies in pursuing its objectives in Europe, such as ending economic sanctions or undermining European support for Ukraine.”
RT, otherwise known as Russia Today, has been embroiled in a series of controversies over the neutrality of its coverage.
In 2014 two of its Western news anchors resigned live on air in protest at Mr Putin”s invasion of Crimea, with American journalist Liz Wahl saying: “Personally I can’t be part of a network funded by the Russian government, that whitewashes the actions of Putin. I’m proud to be an American and believe in disseminating the truth and that is why, after this news cast, I’m resigning.”
The channel has also previously been sanctioned by Ofcom for biased reporting on the conflicts in Ukraine and Syria.