Gordon Brown's favourite children's book is The Snail and the Whale, which describes how a tiny snail hitches a ride on a humpback whale. Together they tour the world, passing icebergs and volcanoes, sharks and penguins. The snail begins to feel very small and powerless compared to the world he sees. But in the end, when the whale is beached, it is the snail who saves his life.

The question is - when it comes to public service reform, is the Prime Minister a slow and cautious snail or a speedy and powerful whale? It is perhaps revealing that in Mr Brown's choice of bedtime reading for his sons, it is the snail who wins.

In the weeks before Mr Brown moved into No10 he used to ask journalists, plaintively: “What do I have to do to convince you that I'm a reformer?” He knew - and he still knows - that the reputation he acquired as Chancellor of being a “roadblock to reform” would be deadly at the next election with voters who increasingly want value for money from the public services. After years of trying to stop Mr Blair being too radical on schools and hospitals, he has spent his first year as leader apparently trying to trump him.

Yesterday Lord Darzi of Denham's report on the health service called for hospitals to be funded on the basis of the quality of their care. In recent months, Mr Brown has announced an expansion of the city academy programme, published eye-catching proposals on the environment and called for large sections of the welfare state to be handed to the private sector. In a report published by the Cabinet Office last week he even said that he wanted to build on the “success of the foundation trust model in the NHS” and create a “growing role for independent public service providers, voluntary organisations and social enterprises” in the provision of public services.

When Mr Brown was at the Treasury he did all he could to block the creation of foundation hospitals - before one crucial Cabinet meeting he circulated a 100-page document detailing everything that was wrong with them. He shredded David Freud's proposals for welfare reform and was reluctant to support Adair Turner's ideas for transforming the pensions system. He was deeply sceptical about opening up the education system to other providers. One Cabinet minister recalls the extraordinary lengths to which Mr Brown went to avoid even stepping through the door of a city academy when visiting a constituency in which it was clearly the best school. At a moment of particular tension with Mr Blair about the role of the private sector in the provision of public services, Mr Brown made a speech emphasising the “limits of the market” in hospitals and schools.

Has he changed his mind or is he guilty of political opportunism? It is hard to avoid coming to the conclusion that Mr Brown was so angry with Mr Blair over the leadership that he wanted to cause trouble. As one Downing Street aide says: “By the end, if Tony was in favour of something, Gordon was on principle against it.” As Chancellor, Mr Brown was positioning himself to the left of Mr Blair to curry favour with the Labour Party. Now that he is Prime Minister, he is positioning himself as a moderniser to appeal to the wider electorate.

The problem is that this makes it difficult for him to sound authentic when he talks about public service reform. As one Labour insider says: “It's like he's talking English as a second language when he talks about reform. It's slightly off key.”

Certainly, there are differences of tone with his predecessor. While Mr Blair emphasised the importance of excellence, Mr Brown emphasises fairness too. He is more cautious about proposals that could create inequalities and therefore less ideologically committed to market reforms. The Blairite watchword was “choice”, the Brownites want people to have a “voice” - through local consultations and customer satisfaction surveys for example.

“For some services increasing choice is not the only or best course of action to raise performance,” the Cabinet Office document states.

I am told that Lord Darzi originally wanted to propose in his report that people with chronic conditions such as diabetes or asthma should be given an individual budget with which to fund their own care. This would have been a significant transfer of power to the patient - but it was seen as risky by the Department of Health and No10 who feared the feckless might blow the money on a Caribbean tour.

Instead, there will be a pilot scheme - although the surgeon-minister played hard ball and managed to get the words “with a view to national roll-out” inserted into the document at the last minute.

There is a similar ambiguity about schools. Mr Brown has announced his intention to “accelerate” the city academies programme - but many of the key freedoms given to them by Mr Blair have been watered down. City academies will in future have to teach the national curriculum, lose flexibility over their staff and be brought more under the control of local education authorities. Ed Balls is also keen to create dividing lines with the Conservatives by waging war on faith and grammar schools - to the intense irritation of his Blairite schools minister Lord Adonis. Mr Blair's view was that excellence would trickle down the system, Mr Brown wants equity enforced across the board. It is a subtle but important shift.

One Cabinet minister says: “Gordon is not doing a U-turn but he has moved into the slow lane.” Another believes that there is a tension between Mr Brown's head and heart. A senior civil servant, who works closely with him, is more blunt: “He fudges everything.”

As a result, the message is confused. On the public services, as on the economy Mr Brown is trapped by his own past. He spent so long playing the role of the snail that he cannot now look like a natural whale.

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