David Cameron and Barack Obama were facing calls on Thursday night to take financial action against Roman Abramovich, the Chelsea FC owner, over Russias annexation of Crimea.
A prominent Russian opposition politician said Western governments response to the Crimean crisis should include seizing the assets of wealthy Russian businessmen, including Mr Abramovich and Alisher Usmanov, a major shareholder in Arsenal FC.
So far, Western sanctions imposed in protest at Russian aggression in Ukraine have fallen on Russian politicians and officials.
But Alexei Navalny, a leading critic of Vladimir Putin, said the sanctions should be aimed at billionaire oligarchs with close links to the Russian president.
Mr Navalny said the West should take action including freezing the oligarchs financial assets and seizing their property.
In an article in the New York Times, he called for action against a list of businessmen including Mr Abramovich and Mr Usmanov.
Neither man has any public connection to Mr Putin or the Russian government.
Mr Abramovich declined to comment. He is understood to consider himself a private citizen with no connection to the Russian government, meaning there should be no question of sanctions being applied to him.
The White House on Thursday night imposed sanctions on at least half the names on Mr Navalnys list including Mr Putins right-hand man, Sergei Ivanov. However, neither Mr Abramovich nor Mr Usmanov faces any action from US authorities. Nor has Britain taken any action against them so far.
Government sources said there was no question of sanctions against the pair. Britain is targeting action solely on people involved in fomenting trouble in Ukraine, a source said.
Brooks Newmark, a Conservative MP, said Russian oligarchs should be included in an expanded sanctions regime.
It is better to focus on the money men around Putin, he said. That would hurt Putin far more than attacking a bunch of politicians. The oligarchs are where the real power lies.
Parliamentary support for targeting the oligarchs is growing, Mr Newmark said.
There is a general feeling that we should be tightening the noose around those closest to Putin.
Dr Andrew Foxall, director of the Russian Studies Centre at the Henry Jackson Society think tank, said there was a legitimate case for sanctions against Mr Abramovich and other oligarchs because they help keep Mr Putin in power.
We know that Abramovich is part of Putins inner circle, he said. There is a case to argue that, like Crimea was Ukraines soft underbelly, the oligarchs are Putins soft underbelly.
London is where they have their property, where their assets are, where their wives shop and their children go to school. Without the support the oligarchs give to Putin he would not be in power.
