Today I announced that I am standing as leader of the Labour party. I did not make that decision lightly. The issue at stake is not just the future of a great political party, but ensuring Britain has a viable alternative government at a time of momentous change.

These are dark times for Labour. And as we navigate a future outside the European Union, they are dangerous times for our country.

I have been a party member since the age of 16. When I became an MP 24 years ago, I did so to provide the same opportunity to others that I was fortunate enough to enjoy myself. We can’t do that if we’re not in government. And we can’t hope to do that if there is no real prospect of us being in government in the foreseeable future.

It is our duty to ensure that the new prime minister, Theresa May, faces a credible and forensic opposition, and to offer a bright future for our damaged economy and fractured society. We are the only people who can hold this rightwing Tory government to account and replace it by winning a general election.

We’re simply not in a position to do that at the moment. Jeremy Corbyn can’t provide the leadership this huge task needs. But that’s not just my view: it is that of the vast majority of my colleagues at Westminster – MPs who were elected by 8 million British people to defend their interests. And, crucially, it is the view of voters I speak to up and down the country.

I believe I can provide that leadership, and I know I can unify our party in the process too. I’m no Blairite, Brownite or Corbynista. What I am is my own woman, someone rooted in our party, and someone who knows how much a force for good Labour has been in office and can be in the future.

But if we are to succeed, we need to concentrate on the politics of hope, not on grievance and blame. That’s the only way we can deliver on our principles of equality, social justice and social mobility.

We need practical socialist policies to heal the divisions and address the uncertainties created by the referendum

That’s my practical socialism, and that’s the sort of socialism that has helped us deliver in government, from the NHS to the minimum wage to cutting child poverty. Real change comes from translating our values into policies that can win popular support.

What’s been so extraordinary about Jeremy is that after taking the leadership he has done so little with it. He has not brought forward practical policies to deal with the problems Britain faces. Instead he harks back to a 1983 manifesto that almost saw us annihilated.

We need practical socialist policies for today, to heal the divisions and address the uncertainties created by the referendum. The leave vote – often strongest in traditional Labour areas – was a message from millions who felt no one had listened to them for a long time.

Theresa May will shortly start negotiating our future outside the EU. We must be clear: the consequences of Brexit must not be dumped on those Labour communities who have already suffered the most from Tory cuts. I was appalled to hear my party leader on TV the morning after the vote demanding the immediate activation of article 50, which would have led to a countdown to exit. I don’t think even Nigel Farage was calling for that.

We need to work for the real interests of working people, who have most to lose if May gets it wrong. That’s why I will demand that the UK government enshrine into the post-Brexit arrangements a commitment to the same labour standards as Europe. We need to compete on skills and ingenuity, not on sacrificing workers’ rights in a race to the bottom.

I want to give the millions of people who voted Labour – and the millions more who would like to do so again – the hope that the party can be an alternative government, ready and equipped to serve. We need to be brutally honest and recognise that the country does not believe that, when they look at us right now. But they will if I win this fight.