Russia's president, Mr Vladimir Putin, has demonstrated beyond doubt that he is the boss of all he surveys by sacking the man long regarded as untouchable - tycoon Mr Rem Vyakhirev, head of the country's biggest company, Gazprom.

But the choice of successor to run the gas giant - a former energy minister - has left western business wondering whether Mr Putin is serious about reform.

Gazprom is more than a company. It is the biggest gas firm on earth, controlling one-quarter of the world's reserves. In Russia, it is a mighty powerhouse with interests spread beyond the field of gas to include hotels, airlines, TV stations, and even a chain of farms and slaughter houses.

Mr Vyakhirev, a gruff former gas engineer, was given the top job when the company was created in 1993 from the shell of the former Soviet gas provider.

Since then, it has worked closely with successive Russian governments, providing clout and support in exchange for having a free hand to control 99 per cent of Russia's gas business. The government had for years given the votes from its own 38 per cent stake in the business to Mr Vyakhirev.

He used that stake to build the company into a personal empire famed for its secrecy - and its allegations of scandal.

Last month came revelations that company executives have transferred millions of dollars worth of assets into companies owned by their families.

A group of minority shareholders, led by flamboyant former finance minister Mr Boris Fyodorov, are demanding investigations into Gazprom's relationship with an offshore gas company, Itera.

Florida-registered Itera has become the seventh-richest gas company in the world, largely due to being sold Gazprom stock on extremely favourable terms. Its refusal to name its owners has led many to speculate that these are related to the Gazprom managers.

None of this would have mattered except that the company is losing money: its profit of $2.1 billion (€2.5 billion) last year was considered poor by analysts, but explanations are impossible as the company refuses to open its books.

More to the point, Gazprom's position above the law is seen as a block along the road to reform by western investors, whose cash Russia desperately needs.

This angered the new president, Mr Putin, a former KGB agent elected on a promise to clean up Russia's corruption and open its markets.

In an apparent bid to keep his job, Mr Vyakhirev ordered Gazprom to take control of Russia's only independent TV network, NTV, earlier this year, silencing a major critic of the Kremlin.

Mr Putin had other ideas. In a deal apparently concluded only days before, shareholders voted unanimously to replace him with former deputy energy minister Mr Alexei Miller last week, the deal being done in a 40minute meeting in the company's gleaming blue and grey glass Moscow headquarters.

Mr Miller has little experience of either big business or gas but is an old friend of Putin.

This caused a slight jump in shares, with investors glad that at least something was being done. But the champagne will remain on ice for now.

"Obviously more is needed. Just changing the guy at the top does not produce anything," said gas analyst Mr Ivan Mazalov of Moscow consultants Troika Dialogue. "There is a lot of optimism that this is a step in reforming the company. The problem with Gazprom is you have to clean out the company before you can begin to reform it."

For Mr Vyakhirev, there is the consolation of being made company chairman. He has now begun to eat humble pie. Previously, he liked to boast of despatching flunkies in the company jet to pick special tundra grass to feed the reindeer on his private Moscow estate.

After his sacking he said: "I'd like to manage a farm. God willing, I'll have a cow shed, a decent stable, hen house and sheep."

For Gazprom, the next weeks will be vital. The company's annual general meeting comes at the end of this month, with Mr Fyodorov likely to repeat demands for a full opening of the books.

The ball is now in Mr Putin's court, with the world waiting to see whether he sees state control of Gazprom and other monopolies as an end in itself, or as a stepping stone to the creation of a genuinely free market.