It is nearly a year since Labour lost the London mayoral election. We should, of course, not forget that, in both the mayoral election and those for the Greater London assembly, Labour performed better in London than elsewhere in the country. Indeed, in the GLA elections we not only gained an additional seat, many of our incumbent candidates increased their majorities.

Nonetheless, we also have to accept that in politics you win or lose, and we lost. We did so because our electoral support was not strong enough, and our appeal not wide enough, to defeat the Conservatives. Looking at the results, it is clear that, very particularly, this was due to our loss of support among aspirational working-class voters in their 30s and 40s, many of whom live in the outer London suburbs.

But the lessons of the past are only worth examining in so far as they inform our understanding of the future. So we should now focus firmly on that future and have an open, honest and searching debate about the policies which can forge a new, winning progressive coalition, one which will return Labour to power in City Hall in three years’ time.

We must begin by listening a little harder, not just to those who voted for us, but also to those who didn’t. Our challenge must be not simply to turn out more of our own voters, but to broaden our appeal and win over new supporters.

And we must accept, too, that when the people of London chose who to vote for, they did so for a reason. We were not relevant enough to their hopes and fears, the things that matter to them. So while our values are enduring, our policies must change to reflect what the voters are telling us. That’s the New Labour way and that’s the only way Labour will remain relevant to London. It is us, not the voters, who need to change.

But what kind of change do we need? As we shape and debate our future policies I believe we should subject them to four progressive tests.

First, do they promote aspiration? What is progressive politics for if not to help people achieve the ambitions and dreams they cherish for themselves, for their loved ones and for their communities?

We have to understand, too, that our goal of opening up opportunity and prosperity to those currently shut out of it – the children and young people growing up in tough Brixton estates in my constituency, for instance – cannot be realised by government alone.

A dynamic, entrepreneurial economy in London demands a London that is open to business, to social enterprise and to the voluntary sector. One that encourages and welcomes private investment and supports business startups, particularly among poorer minority ethnic groups, in those parts of the capital where it is all too lacking but needed the most.

We have to be honest: the aspiration agenda will present us with dilemmas. Take the green agenda. We are right to champion sustainability but the way we talked about green issues last May put people off. Many Londoners rejected the westward expansion of the congestion zone not because they did not share our aspirations for a greener London, but because they feared we just wanted to tax them more or prevent them owning a car. It is no good us telling voters their views are unreasonable – it’s our job to reconcile the tensions and come up with something attractive and new.

Second, do our policies make Londoners feel safer in their homes and on their streets? Last May, crime was judged the most important issue by Londoners in deciding how to cast their votes. But despite our strong record, Boris Johnson convinced more Londoners that he understood their fears and would address their concerns. He talked about crime in the terms that people talk about it to each other.

We will not connect with people unless our language, like our concerns, is the same that people hear on the streets, outside the school gates and in the living rooms of London.

Today, crime and antisocial behaviour remain second only to the economy as the most important issue for Londoners. So we must now be relentless in making Boris defend his record and we must set out an alternative agenda that shows we are truly in touch with Londoners.

That agenda must recognise that tackling crime and expanding opportunity go hand in hand. The Tories choose to demonise young people. Our job is to protect those young people who are most at risk of being victims of crime while offering an alternative path to those young people who are most likely to commit it.

Third, do they empower the people of London and the communities in which they live? Running through our entire agenda there must be a common thread and a simple question: what does this do to place greater control in the hands of Londoners and their communities?

While it may be popular in the world of thinktank seminars, empowerment is not a word that excites. Indeed, this is a subject that can sound like hot air – until we acknowledge that the real solution to so many of our problems lies in the communities that are most affected. Talk to people on estates about youth crime and they will tell you what needs to be done. Now let us find new ways to hand those people the power and the resources to take control and make that change happen.

Finally, do they bring London together? The people of London know that the diversity of our city is our greatest strength. We love the fact that we have the whole world within the borders of a single, great city.

But while recognising difference, our political appeal must transcend it and our coalition must be one that is united by shared interests and values. That means we have to be as attentive to the attitudes and aspirations of zone six as we are to zone one. As a party, we need to understand the importance of every community, but recognise that they all fit into a London that is bigger than the sum of its parts.

So let’s step outside our comfort zone. Let’s listen to the voters and let their concerns and our values forge together in a new progressive agenda that is relevant to London.

And for me, the measure of our success will be easily judged: not simply in terms of whether we return a Labour mayor to city hall in 2012, but whether they are able to win right across the capital and not just in our heartlands.