All eyes are on The Date. When will Tony Blair leave No 10? The media are fixated with it. Many in the Labour party appear equally addicted. They are focused on the wrong thing. It is not the date of Blair’s departure that will shape the future of British politics. It is The Debate about what happens when he does depart.

Of course, the obsessing about the prime minister’s longevity reflects a mood of uncertainty among Labour MPs. This period is Labour’s toughest in almost 10 years of office. Controversy over Iraq, Lebanon and aspects of domestic policy have combined to produce a clamour from some quarters for Blair to go — and go now. Or, if not, to name the date.

It is as if Blair alone is the problem and his departure is the sole solution. Ominous warnings of a Thatcher-style frogmarched exit are being sounded. Of course, such dark threats conveniently forget that when Margaret Thatcher left Downing Street the Conservatives were more than 20% behind in the polls. And whereas she was going on and on and on, Blair — uniquely for any prime minister — has said that he is not. As he reiterated last week, instead he will give ample time for his successor ahead of the next election. He is right to resist pressure to go any further.

There is a different lesson that Labour should draw from Thatcher’s downfall. I became an MP in 1992 shortly after the transition to John Major. Oddly enough, amid the despondency of a fourth Labour election defeat I felt hope. Looking across at the Tory benches in the House of Commons I saw a party fatally wounded by divisions over direction and a mish-mash of policy. In their headlong rush to change their leader the Conservatives had failed to resolve or update what they stood for in a changed world. They went for the date but avoided the debate. Electoral catastrophe inevitably followed.

In other words, electing a new leader is not a political panacea. Replacing Blair will not in itself renew Labour. Renewal means more than changing the guard. It means updating policy and purpose so that it is in tune with the modern world. That requires the debate.

Here, too, there are important lessons from the recent past. After our 1992 defeat many thought that Labour could never win again. What changed was that we did. Building on the legacy of Neil Kinnock and John Smith, Blair’s courage in radically changing his party was the crucial step that took us to power.

New Labour was created around the insight that for progressive values to be realised they had to be applied in new ways. And after almost a decade in power — notwithstanding obvious problems — Britain feels stronger and fairer as a result. Poverty has declined. Wages have risen. Prosperity has increased.

New Labour was formed as a modern centrist progressive party through a genuine process of debate and renewal — not just a new leader but a new constitution, new politics and new policies. After a decade in office it is time to debate and renew again. The priority now is to determine Labour’s post-Blair purpose and policy. And to do so before any leadership contest.

The debate should be open to allcomers. The public would look on askance if Labour’s future policy direction was hammered out behind closed doors or by a block vote rather than through an open process. Reconnecting government policy with how people live their lives today requires more transparent politics, involving not just all parts of the Labour party but the wider public as well. The debate can serve to demonstrate that Labour is in touch and has wind in its sails.

There is, and can be, no monopoly on wisdom. Recent contributions from Gordon Brown, Stephen Byers and Charles Clarke reflect the start of the unstoppable process of discussion about what that future will hold. I suspect that Labour’s conference later this month will see a further flowering of ideas and proposals, particularly from the new generation of younger ministers and MPs. In particular it is incumbent on all those with ambitions to lead (or deputy lead) the Labour party not just to throw their hats in the ring but also to put ideas on the table. A Trappist vow of silence will not work.

The debate is something to welcome, not fear. Of course there are dangers in every contribution being seen through the Blair-Brown media prism. Everyone is acutely aware that split parties lose elections. The best way of sidestepping that trap is to avoid the nonsensical notion that debate is somehow factionalist. Charting a course for the future is not a luxury, it is a necessity for any party serious about winning. Indeed, it would be faintly bizarre if the Labour party after a decade in government did not have a debate about the next decade.

The challenges that new Labour faced in 1997 are very different from those faced today. By way of illustration you only have to look at the leftist bible of the mid-1990s, The State We’re In by Will Hutton, with its plea for a new marriage between economic vibrancy and social justice. That has been new Labour’s motif for a decade or more.

Or take the challenges that Peter Mandelson, one of new Labour’s principal architects, identified in The Blair Revolution which he co-authored 10 years ago: economic prosperity alongside reforms in health, education and welfare systems, constitutional change and a new relationship with Europe. People may quibble about the detail but in good part these challenges have been met.