Russian prosecutors today began questioning the jailed oil tycoon Mikhail Khodorkovsky on a new set of embezzlement charges, which would appear to augur badly for hopes of his early release.

Dmitry Medvedev, the new President, has yet to make his position clear regarding the former oligarch, widely seen as a political prisoner. Observers say that the next steps in the case will show how serious Medvedev really is about battling what he has called Russia's “legal nihilism”.

Now in a remand prison in Chita, 4,000 miles east of Moscow, Khodorkovsky was charged all over again, together with his business partner, Platon Lebedev.

“Investigators of the Main Investigation Department have brought new charges against Khodorkovsky and Lebedev: charges of large-scale misappropriation and legalisation of money earned through criminal activity,” the Prosecutor General's office said.

Khodorkovsky and Lebedev stood accused of “misappropriating nearly 350 million tonnes of oil and laundering 487 billion rubles (£10 billion) and $7.5 billion (£3.8 billion) in cash”, it said.

“The defendants are being questioned on the charges brought in the presence of defence lawyers.” Khodorkovsky's defence team, who learnt of the new charges yesterday, said they were “the same old collection of absurd and unproven allegations”.

Khodorkovsky, 45, formerly head of the Yukos oil company and at one point Russia's richest man, was convicted in 2005 of fraud and tax evasion and jailed for eight years. A man with opposition leanings, he was widely seen as a victim of President Putin's pique. His incarceration in Siberia marked a watershed in how the West regarded the Putin regime.

Prosecutors had been threatening for some time to weigh Khodorkovsky down with new charges but until today's confirmation that the accusations had become formal, the general talk was more about the possibility of his early release.

Khodorkovsky himself has always refused to ask for a Kremlin pardon, as that would imply guilt and he stmaintains his innocence. His lawyers last week encouraged him to apply for parole on the ground that he had served more than half his sentence (counting time spent in pre-trial detention from 2003) and he said that he would think about the proposal.

Although he is far away — out of sight and mind as far as his enemies are concerned — his profile has been raised lately. On his birthday on June 26, supporters in various Russian cities cleverly avoided trouble by toasting him at “street parties” that the authorities were unable to classify as demonstrations because no banners were unfurled.

And the German Government quietly raised his case when President Medvedev visited Berlin in June. Afterwards, Khodorkovsky's supporters expressed hope that he might at least be moved from Chita to Moscow, where his wife and elderly parents could visit him more easily.

Seen in the context of these moves, the prosecutors' decision to bring new charges may perhaps be a desperate act.

Khodorkovsky's defence team said that the charges looked like a procedural move to buy time. “The defence can find no explanation other than the prosecutors' lack of certainty — bearing in mind changes that have taken place at the top of the Government — and their desire to play for time in the hope of receiving…support from the top.”

All eyes will now be on President Medvedev, who has generally adopted a softer tone of voice if not softer policies than his predecessor and mentor, Mr Putin. Sparing Khodorkovsky would be the biggest single thing President Medvedev could do to show that he is his own man and not merely the puppet of Mr Putin, who is now Prime Minister.

Khodorkovsky's mother Marina, denying Russian tabloid reports that her son was seriously ill, suggested he was ready to fight on. “He has a slight allergy, possibly caused by the absence of sunlight, but he is not complaining about his health,” she told Echo of Moscow radio. “His morale is high and he is in a steely mood.”

Times Recommends

• Google to digitise Iraqi artefacts
• Renault angers parents by naming new car Zoé
• Analysis: most lawless part of Philippines