Jailed oil tycoon Mikhail Khodorkovsky has said Russia's next leader may not be able to undo the damage done to the rule of law in the Putin era.
Mr Khodorkovsky, once Russia's richest man, said the lack of the rule of law was his country's biggest problem.
The ex-boss of Russia's disbanded oil firm Yukos was speaking to the Financial Times, in what was his first face-to-face interview in five years.
Mr Khodorkovsky was sentenced in 2005 to eight years in jail for tax evasion.
His supporters say the charges were politically motivated because he funded Russian opposition groups.
Mr Khodorkovsky, 44, is currently on hunger strike in support of another Yukos executive, Vasily Aleksanyan, who is being tried on embezzlement charges.
Mr Aleksanyan has Aids and cancer - and on Thursday the authorities said he would be allowed out of prison for specialist hospital treatment.
Mr Khodorkovsky was speaking in a courtroom in the eastern Siberian city of Chita, where he is being held to face new embezzlement charges.
He accused President Vladimir Putin of using the law to target political enemies, especially business owners like himself.
He expressed doubts that Dmitry Medvedev, Mr Putin's chosen successor, would be able to reverse the trend.
"It will be so difficult for him. I can't even imagine...
"Tradition, and the state of people's minds, and the lack of forces able to [support] any movement towards the rule of law, everything's against him. So... may God grant him the strength to do it. All we can do is hope," Mr Khodorkovsky said.
He identified Russia's biggest problem as the lack of the rule of law, saying it was worse than in China.
"Laws can be better and they can be worse. But people must abide by laws, and not use them for their own ends," he said.
However, he said he was generally optimistic about Russia's future, adding that it was "not possible" for his country to return to the darkest days of its Soviet past.
"I'm convinced that Russia is a European country, it's a country with democratic traditions which more than once have been broken off during its history, but nonetheless there are traditions."
Yukos, once Russia's biggest oil company, was declared bankrupt in 2006 and ceased to exist as a legal entity in November 2007.
The company had been steadily dismantled after being accused of massive fraud and tax evasion by the Russian authorities.
Yukos maintained it was the victim of a concerted political campaign by a government which wanted to discredit its executives and gain control of vital energy assets.
Russian officials deny the allegation.