May 4? June 6? July 1? The Kremlinology and kidology, never mind simple betting, around the date of Tony Blair’s departure from No 10 seem endless. But I honestly don’t believe that the departure date makes an iota of difference to the future of the country or the Labour Party. It is a substitute for serious thinking, because “when?” matters far less than “what then?”.

PostBlair politics is virgin territory. For ten years the Tories as well as (large) sections of the media and (small) parts of the Labour Party have comforted themselves with the idea that Tony Blair was Britain’s problem, and his departure the answer. But new leadership is the easy bit. Soon we are not going to have the Prime Minister to kick around any more, and life is going to be tougher.

Even without boundary changes, which apparently represent a net gain of between a dozen and two dozen seats to the Tories, Labour’s challenge is easily stated: to be bold Labour, not old Labour. Experience and competence are necessary, but insight and ideas provide the critical difference between success and failure for a Government seeking a fourth term in office.

We obviously cannot and will not go back on the red lines established by new Labour — for example about the economy or national security. But continuity with the Blair years is not enough. Britain has changed since 1997 — of course not perfect, but richer, fairer, more confident. The Tories claim to have made their peace with our reforms; we who created new Labour need to take it into new areas.

We must respond to emerging aspirations and fears, from migration and terrorism to elderly care and getting on to the housing ladder. But as well as broadening our agenda, we must deepen it. For example, people still talk about a trade-off between protecting the environment and boosting the economy. We need to expose this false choice. To do so we need to renew the relationship between politics and markets.

Climate change is, according to Sir Nicholas Stern, the greatest ever market failure, but the answer is not to replace markets. Instead, we need to price pollution into markets and extend market mechanisms so that they work more effectively. If we are to uncover the most efficient carbon reductions, the long-term aim must be for carbon trading to cover the vast majority of the UK economy, with a price on pollution enforced through markets, taxation and regulation.

Climate change also requires a much deeper commitment to EU and international action. By using the power of Europe as a single negotiating block, we can help to forge a post2012 framework. By extending the European Union Emissions Trading Scheme, we can make it the basis of a global carbon market. By regulating across Europe — for example, setting a date when all new power stations are carbon neutral, or driving up car emission standards — we can move to a low-carbon economy without suffering competitive disadvantages from acting alone.

Climate change does require tough decisions. But some of the most difficult choices are between different environmental goals. In the context of climate change, environmentalists (and conservationist conservatives) will have to question some of their traditional positions, whether on nuclear power, expanding wind power or the use of agricultural land for biofuels.

Labour needs equal boldness elsewhere. On the back of every Labour membership card it says that our goal is a country where “power, wealth and opportunity are in the hands of the many not the few”. The Government has extended opportunities in education and employment; we have taken useful measures to help to spread wealth; we need more of both; but we also need much more radicalism in redistributing power.

The starting point must be to devolve power right down to individual citizens. That is what personalisation and extending choice is about. It is an ambitious vision in public services, but we need to define it more clearly and accept that achieving it will mean major changes in budgets, institutional structures and professional roles. Personalised services should be as inspiring for new Labour as privatising services was for the Tories. The next phase includes devolving budgets down to users and families and giving frontline workers far more flexibility to respond creatively to citizens’ demands.

However, many things we care about are collective in nature — from the cleanliness of streets, to the quality of public transport, to crime prevention. These need collective action. In 1997 constitutional reform dispersed power to Scotland, Wales and London. In 2007 we should map out the economic, social and cultural transformation that can be led by empowered towns and cities.

There is no lack of great causes. They are just different from 1997. By deepening our agenda and adopting radical solutions we can capture the sense of idealism that is Labour’s unique selling point — “a moral crusade, or it is nothing”, as Harold Wilson memorably (and rather out of character) said.

This requires not just new leadership and new strategy but new culture. We need to connect our Government and our party with the activism and energy often found in movements outside formal politics, from environmental groups to social entrepreneurs. Of course, this means exposing complexity and doubt, escaping from the false comfort of “lines to take”. But that is the new politics, based on dialogue rather than “message”.

The choice at the next election could be stark. On the one hand a Tory leadership hiding what it believes in, desperate to persuade voters that what they have gained under new Labour will not be threatened. On the other hand, a Labour Party confident of its ideology, urging the public to sign up to an ambitious vision of modern Britain. I know which side I would prefer to be on.

David Miliband's blog is at www.davidmiliband. defra.gov.uk

Times Recommends

• Can I be complimentary, my dear Watson?
• Hardliners realise Britain is a soft touch
• The jaw-dropping truth about Gordon