The Labour Party is disunited. The events surrounding the Cabinet reshuffle over the past few days could not have illustrated that more graphically. As a result we are weakened and distracted, facing the twin crises of the economy and the reduction in public trust in our parliamentary system.

Unity comes, ultimately, from leadership; the party will follow. There will always be people who attack the leader, but the mainstream will follow a clear and decisive direction reflecting the values of the Labour Party.

My view is that the painful step of changing our leader, a leader who has given his life to the Labour Party and to public service, would be best for the party and the country. The choice is for the Prime Minister and the party. I believe that if we change, then we would go into the next election, whenever it was, so much stronger.

We urgently need to address this issue. Without clear direction the public will have so comprehensively written us off in their minds by the middle of next year, when the election is expected to take place, that recovery will be very difficult.

Gordon Brown faces a wholly new political situation from the one he inherited in 2007. It requires humility and the ability to change fundamentally in the eyes of a public fed up with and distrusting of the political class. It requires leadership different in type and culture from that which has gone before: more openness; a greater willingness to rely on a wider range of people; more explanation - as well as being focused on and frank about the economy.

It needs the leader to be the driver and the agent of very big change. This needs highly developed leadership skills. Gordon Brown has not displayed those skills.

My fear is that, in the face of this task, Gordon will find it difficult to carry the mainstream of the Labour Party with him. James Purnell, Nick Raynsford and Barry Sheerman all come from different parts of the party. All their interests and their instincts would be to follow the leadership of the party that they have each served for decades.

But each one of them is calling for leadership change because, like me, they believe that it is hard to unify under the current leader. All of us will have heard the activists who rail at those within the party who attack the leadership. That argument would normally prevail. But not in the current situation because it is so difficult for Gordon Brown, after 12 years as Prime Minister or Chancellor, to be a convincing agent of change.

And a change of culture in the way government is done is urgently needed. The message of the expenses scandal is that the public will not accept government being conducted in secret by a handful of people. There needs to be a much more open discussion of the issues. Only with that openness can trust gradually begin to be rebuilt.

That new openness needs to apply to Gordon's leadership. No plots. Instead debate. I am only one voice in this debate. These are very difficult judgments. But they matter so much to the future of this country and our party. We should debate this without rancour.

Our party does not lack credible, heavyweight figures. The reshuffle, with all its hiccups and resignations, produced a very strong Cabinet. Alistair Darling, David Miliband, Alan Johnson, Peter Mandelson, Jack Straw and Harriet Harman are each powerful, competent, front-rank figures. The new entrants into the Cabinet included Andrew Adonis, Bob Ainsworth and Ben Bradshaw. Each of them is a substantial figure. Bob Ainsworth, for all the sneering in the press, is someone whom his fellow politicians, civil servants and the Armed Services greatly respect.

And, but for our weakness, the Tories would be vulnerable. They scored only 38 per cent in the local elections, at a time when the governing party has been in power for 12 years. So we have the personnel. And the Opposition is not, yet, locked-in for victory in the next general election.

We have an opportunity. The best talent in our party could contest a leadership election - people such as David Miliband, Alan Johnson, Jon Cruddas, Harriet Harman - and we would then rally round whoever was the winner. That contest would allow the discussion we need to have about the direction of our party. And we could reconnect with the public; it would be the basis for a re-establishment of trust. The cloud of disunity and despair haunting our party would, I believe, lift.

None of this ensures we would win the next election. We would have to fight for that and for trust. But we would have renewed, at a time when politics could not seem more disengaged from the public. We would have listened, and we would have acted. We would be for the future. More of the same is no longer tenable.

While there is no constitutional requirement to have a general election after selecting another leader, there would be significant political pressure. But if there were important steps going on to clean up politics, for example, or initiate progress on parliamentary reform and change supported by other parties, then there would be a proper basis for waiting. It would depend on the new situation, and when the change occurred.

Would we go to the country under the shadow of the expenses scandal? It would certainly play its part. But as a party we would have shown our understanding of the need for profound change by choosing a new leader and adopting the direction given by that new leader.

Whatever the length of time under this new leader, we would be more strongly united around both a new leader and an agreed programme, rather than clinging, disunited and dissatisfied, to the present position.

Lord Falconer of Thoroton is a former Lord Chancellor and Secretary of State for Justice

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