The respected business daily Vedomosti quoted unidentified Kremlin sources as saying that Dmitry Medvedev, the current president, could step down after carrying out changes to the constitution that would allow Mr Putin to solidify his grip on power.

In his first state of the nation address on Thursday, Mr Medvedev proposed amending the constitution to allow sitting presidents to stay in power for 12 rather than eight years.

Mr Putin served as Russia's president between 2000 and May this year, but was forced to shoehorn Mr Medvedev, long his protege, into his job because of a constitutional provision that barred him from serving more than two consecutive four-year terms.

Since May, Mr Putin has been Russia's prime minister, but many believe he remains the country's most powerful man and are convinced that Mr Medvedev is little more than a cipher.

Speculation abounded last year that Mr Medvedev would be little more than a stopgap leader who would step down once he had extended presidential term limits and undertaken potentially unpopular social reforms that could have undermined Mr Putin's popularity.

A spokesman for Mr Putin denied that there were any plans for an election next year but refused to comment on whether or not the ex-KGB spy had ambitions to return to his old job.