This has been a depressing week for everyone in the Labour party and all who believe in a fairer Britain.
We need to face uncomfortable truths: we lost the election and it was a bad result. Despite the hard work that was done, this is the second worst result for us since universal suffrage.
We can't explain away that defeat on the basis of one person or one moment in a campaign. The reasons for defeat are much more fundamental than that.
Now is the time to make use of the only advantage, frankly, that we get in opposition: the chance to have the far-reaching debate that we did not have in government. I am convinced that if we ask the hard questions as new Labour did in 1994 and the Conservative party did not do after 2005, then we can make sure this is a one-term government.
I will always defend the record of our government because we made this country more prosperous, fairer, greener, more democratic, and we should all be proud of what we achieved. But there is deep thinking we need to do about what went wrong.
For me, there is one central lesson: as government wore on, we lost that sense of progressive mission and of being in touch with people's concerns.
Think about the things we are proudest of: the minimum wage, investment in healthcare, tax credits, Surestart – almost all of those were a result of decisions made in the our first years of government. But gradually, we came to seem more caretakers than idealists – more technocratic than transformative.
Take the economy. We did great things after 1997, but while the New Labour combination of free markets plus redistribution got us a long way, it reached its limits some years ago. And I saw that during this campaign.
Canvassing in my constituency, I met a classroom assistant. She told me she was taking home about £9,000 a year, but wasn't eligible for tax credits because she was working 27.5 (not 30) hours a week. She couldn't afford anything but the necessities of life, and felt we had nothing to say to her. For her, and millions like her, on modest incomes, we need to rediscover our sense of progressive mission.
Another constituent told me he was voting BNP because his friends' wages were being undercut by immigration from eastern Europe. Britain's diversity is an enormous strength: economically, culturally, socially, and we should say it more often. But the truth is that immigration is a class issue.
If you want to employ a builder, it's good to have people you can take on at lower cost, but if you are a builder it feels like a threat to your livelihood. And we never had an answer for the people who were worried about it.
We need to rethink what it means to make Britain a fairer country. Over time, the connection between our sense of fairness and people's sense of fairness frayed – we need to acknowledge that. It frayed over excesses at the top; and it frayed over the people at other end of society as well.
We showed great radicalism when it came to preventing a rerun of the Depression. But we didn't have that radicalism when it came to dealing with the banks and the bankers. Fundamentally, we were stuck in a mindset of the 1990s, which feared the idea of government taking on the power of markets.
We need to recognise also what people feel about the state, and their daily frustrations with it. We should take extraordinary pride in the rebuilding we did of schools, the NHS and other public services. But we left too many members of the public feeling the state is indifferent to them – faceless and unresponsive – and public servants who felt that we didn't value what they do and micro-managed too much.
In all these areas, we lost sight of our values and of what people expected from us.
So first, we need a new way of thinking about markets. Globalisation is not an untameable force of nature to which we must adapt or die. We must think anew about how we rebuild economic security in the 21st century.
Second, we need a new way of thinking about the state. David Cameron's "big society" is not a way of solving this problem – it is a recipe for abandonment. We need to show we are the people who can reform the state to make it more accountable and give power away.
Third, we need to show that we get what really matters in life, beyond economics: climate change and the environment need to be central, not an add-on, to our political vision. But family, neighbourhood, community, quality of life, time, love and compassion – all these need to be central to the way we think about politics.
Fourth, we need a new way of doing politics itself. The fact that there is a Conservative-Liberal coalition government should not make us retreat from pluralism and political reform. The old ways of doing politics are a complete turn-off for the public. And we need to face the truth that we suffered a catastrophic loss of trust over Iraq.
A new way of doing politics means we have to think hard about our party, too. The trade union link matters because it is our link to working people in this country. And we need to give party members a proper voice. But we also need to be more outward-looking, to reach out to people in the environmental movement, voluntary organisations and local citizens' organisations.
We need a party that reflects the reality of modern Britain. At all future election campaigns, we must make sure we are a party of women, as well as men. But Labour needs to be not just an electoral force, but also a movement for change. I want to play my part and next week, I will be launching a living wage campaign in Britain.
I joined the Labour party at the age of 17. I joined because I thought it was the best vehicle for the hopes and aspirations of the British people. I believed it then, and I believe it now.
In recent days, several people have talked to me about the contribution I should make in the future. I have talked it over with my family, about what it would mean and I have made my decision. Today, I am putting my name forward to be leader of the Labour party.
Let's move on from the politics of Blairites and Brownites and unite around a new set of ideas. This leadership election cannot just be about leadership candidates. It has to be about you as well.
Ed Miliband, the coordinator of the Labour manifesto, the former energy and climate change secretary and MP for Doncaster North.