An outspoken aide to Russian President Vladimir Putin has offered his resignation in protest against changes in government policy.
Economic adviser Andrei Illarionov said
Russia was no longer politically free but run by state corporations acting in their own interests.
"I did not sign a contract with such a state," Mr Illarionov told reporters.
He has been the most vocal critic in the corridors of Russian power for some time, our correspondent says.
His remarks are seen by some experts as potentially embarrassing for Mr Putin, as Russia prepares to take over presidency of the G8 club of industrialised nations later this week.
'Impossible to remain'
"It is one thing to work in a country that is partly free. It is another thing when the political system has changed, and
the country has stopped being free and democratic," Mr Illarionov told reporters in Moscow.
He said that "therefore it is absolutely impossible to remain" in his post.
Mr Illarionov added that Russia's economic policy and the economic model of the states had changed.
He also said: "Until not long ago no-one put any limits on me expressing my point of view. Now the situation has changed."
Mr Illarionov has recently criticised government economic policy with such gusto that he sounded more like the Kremlin's arch opponent than its employee, the BBC's Steve Rosenberg in Moscow says.
A year ago, he condemned the Russian authorities attack on the giant Yukos as the swindle of the year, our correspondent says.
The Kremlin took away some of his duties, like his role as Russia's representative to the G8, sidelining the respected economist.