Alexei Navalny, prominent opponent to Russian President, Vladimir Putin, has said that Britain has not gone far enough in its proposed sanction of expelling 23 Russian diplomats, following the nerve agent poisoning of former double agent, Sergei Skripal, and her daughter, Yulia, on UK soil.

Navalny who is seen as a political threat by the Kremlin, owing to his detailed uncovering of corruption among Putin’s circle, has been banned from running in the Russian Presidential election on Sunday, March 18, 2018, due to a criminal conviction he says is trumped up.

He told radio station Echo of Moscow that British Prime Minister Theresa May should have done more and targeted rich Russians living in Britain.

This is even as Moscow says it will respond in kind to the U.K.’s expulsion of 23 Russian diplomats over the nerve agent poisoning of former double agent Sergei Skripal.

Russia’s foreign minister, Sergey Lavrov, said the tit-for-tat expulsion of British Embassy staff would take place “soon.”

The Kremlin denies involvement in the nerve agent poisoning, insisting a motive was to complicate Russia’s hosting of the World Cup this summer, Russian news agency Interfax reported.

Navalny said: “I am disappointed because the first speech of Theresa May was rather tough and aggressive. But what they have announced now is such a standard diplomatic action: 23 diplomats will be expelled. Our response, of course, will be to expel 23 English diplomats.

“I’m interested in the 23 Russian oligarchs who will continue to live in London and the 23 Russian officials who will continue to launder money there.

“I would very much like to have, regardless of the Skripal case, English justice. The English government should expel our crooks, or at least stop them from enjoying a comfortable life in their country,” he told the station.

Meanwhile, the Russian Embassy in London said the U.K. could have produced a nerve agent because many Russian scientists have fled to the West, reports Newsweek.