Russia's financial crisis is beginning to destabilise the delicate Kremlin power balance, with a struggle between rival clans eroding Vladimir Putin's authority and aggravating his relationship with his protege, President Dmitry Medvedev.

There are growing signs that a powerful group of military and security officials grouped around Putin are locking horns with economic liberals headed by Medvedev as the two groups fight for control of rapidly evaporating state finances.

Medvedev marked the first anniversary of his election victory yesterday, but the triumphalism has long since dissipated.

Russia has been hit hard by the global crisis, with the stockmarket down almost 80% from its peak, and the rouble sliding fast. Russia's top 10 billionaires alone lost an estimated $150bn last year.

The sudden evaporation of Russia's newfound wealth has set the two Kremlin cliques on a collision course and put Putin - now prime minister - in an awkward position. As a former KGB agent he is heavily identified with the security group, known as the siloviki, but he also has strong personal loyalty to a small clique of liberals from his home town of St Petersburg.

Experts say Putin is losing status as he attempts to contain conflict between the factions. Cracks are appearing in his relationship with Medvedev.

"Putin used to act as an arbiter standing above the two main clans - the siloviki and the rational economists," said Dmitry Oreshkin, a leading political analyst. "Now he's been dragged down into the fight and he's under fire from both sides. The siloviki say he's a weakling incapable of imposing his will and showing the economists their place, while the economists in turn are consolidating around Medvedev."

Medvedev, handpicked by Putin from among loyal acolytes as a successor, has begun to issue muffled criticism of his mentor, leading some to believe that he may be enjoying the trappings of power and be prepared to flex his political muscle.

At a recent meeting with economic officials Medvedev said responses to the financial crisis - set by Putin as head of government - were "unacceptably slow" and instead of action on promised reforms there had been only "talking and talking".

Last month Igor Yurgens, director of the Institute of Contemporary Development, a new thinktank created by Medvedev, criticised Putin for restricting press freedom and stressed that "the most honest and independent opinions on Russia's problems are coming from the liberal wing, rather than from the so-called statist patriots".

"Medvedev has got the whiff of power in his nose and he likes it," said Mikhail Delyagin, an analyst and former government adviser on economic policy. "He's given tacit approval for his administration to engage in an information war with Putin's apparatus."

The man at the centre of the Kremlin power struggle is the finance minister, Alexei Kudrin, who has warned the siloviki and the private corporations in which they have strong interests that the state is limiting financial rescue packages for big business.

"The siloviki have been used to sharing out the spoils of the state," said Delyagin. "They want to get rid of Kudrin because he holds the purse strings and he's not giving them any cash."

An $18m corruption investigation into the finance minister's deputy was renewed three weeks ago in a thinly veiled attack on his boss by the siloviki. For Putin, the problem is that Kudrin - who yesterday admitted mistakes in handling the financial crisis - is one of his deputies and an old ally from his St Petersburg days.

The internecine struggle between Kremlin factions has prompted rumours that Putin, afraid of becoming a focal point of public discontent, recently considered the possibility of leaving his post. In this scenario, he would become speaker of the state duma, Russia's lower house of parliament, as a member of the statist United Russia party. Another scenario is that Putin will be forced to sack Kudrin in order to appease the military-security clique. A former lawyer, Medvedev has no law enforcement links in his past and is at loggerheads with key siloviki figures such as the deputy prime minister, Igor Sechin, who rely on Putin for influence. Medvedev, 43, has little of the physical aura of Putin, 56, who has burnished an action-man image by flying jets, practising judo throws and being pictured going fishing with a bare chest. Commentators, however, say the younger man is slowly gaining authority.

"At the moment Medvedev can still walk into a room full of governors and no one will even notice him," said Delyagin. "It reminds you of Winston Churchill's phrase: 'An empty taxi pulled up at 10 Downing Street, and Clement Attlee got out'. But he is building confidence. And it shouldn't be forgotten that Attlee in fact defeated Churchill."