At three successive elections in the last decade, Labour has failed to address the reasons for its defeat. The consequence is simple. We lose again. The electorate send us back to the classroom. This time, a similar failure, a further relapse into denial, and the result could be fatal for the party and the communities we are supposed to serve. The question for the party is fundamental: are we really serious about getting back into government? If not, then it is the political graveyard not just the classroom that beckons.

In 2010, Labour won eight seats out of 210 in the south of England outside London. But we were told that the problem was the Blair legacy, even though we had won many of those seats in the Iraq-stained election of 2005. We underestimated our opponents and moved into the comfort zone of talking to ourselves.

In 2015, Jeremy Corbyn won the leadership by attacking our time in government. Reforms to the Labour leadership voting system, by limiting the role of MPs, further reduced our connection to the real electorate: voters. The result was a Corbyn leadership which failed to command the confidence of MPs or ultimately the public.

In 2017, a defeat was diagnosed as a victory. We significantly increased our vote share but not our number of MPs against the worst Conservative campaign in living memory. We were sold the category error of confusing opinion poll support for individual policies with support for the programme as a whole.

Now in 2019, the danger is that the excuses outrun the facts again. The voters could not be clearer. It is not only Corbyn who needs to be replaced, but his politics: the ideology, the worldview, the theory of political change.

Labour literally repelled voters in 2019. “Out of touch” does not capture the full awfulness. Voters were all too in touch with what the Labour leadership stood for. Incredible promises were all too well understood. So was the unctuous sectarianism of the leadership clique. Together they came to be seen as more of a risk to the country than Brexit – even though every study shows that it will cost the poorest communities the most.

John McDonnell said at the 2017 party conference that the more dire the situation a Labour government inherits, the more radical would need to be its efforts. Fair enough. The greater the inequality, the greater the need for remediation. There was and is an appetite for a step change from austerity that is serious about redistribution and wealth creation.

But there is a corollary. The greater the proposed radicalism, the greater the credibility needed of the policy and and the plan and the team to make the changes. Labour failed on all counts. Every extra promise weakened the appeal of all the promises.

Credibility is scorned by the hard left. We are told it means sucking up to the establishment

Credibility is scorned by the hard left. We are told it means sucking up to the establishment. Or taking Tory positions. Rubbish. It is about recognising that people with the least have the most reason to be risk averse about taking a chance on the future. And we should take our cue from them. If you are proposing to make a big change in someone’s life, they want to be sure that you know what you are doing. Radicalism without credibility is just posturing.

In America they say an election campaign is an MRI on your character. Yet the leadership culture was toxic. The failure to acknowledge, never mind address, antisemitism is a moral scar. The sectarianism addressed at those who disagreed with the edicts of the leadership was disgraceful. Remember it was only the early election which called off the hounding of MPs with deselection. Eddie Mair called Boris Johnson a “nasty piece of work”. Voters rightly concluded the same about Labour’s hard left.

Of course Brexit was an issue (though smaller than Corbyn and his promises). But the Labour evasions over three years exacerbated the problem. So neither leavers nor remainers were happy. Doing a deal with Europe in three months. Then refusing to campaign for or against it. It did not add up. There is no evidence that Labour MPs who backed a second referendum did worse than those who did not. It was the leadership decision to support the Tory call for an election before Brexit was resolved that was terrible hubris.

The agenda in 2023 or 2024 will have important differences from the present. But the choice of the electorate will be driven by many of the same questions. Whether the values of the Labour leader and top team offer a progressive patriotism. Whether the vision of the party speaks to the real issues facing the country. Whether the plans can be explained, paid for and delivered. Whether the team represents the aspirations of the country. Whether the leader is actually a leader.

Attlee passed this test. So did Wilson. And Blair. Only three Labour leaders have ever won a working majority. Let’s learn from the successes and not split the difference with the failures. It would be absurd to say the policies should be the same. I don’t propose a rerun of 1997 any more than of 1945. But the politics – the clarity, the positioning, the orientation to the future not the past, the capacity to lead – is timeless. That is what I will be looking for in the leadership candidates.

The next leadership team needs to show the British people that they recognise the fundamental errors of policy and character that made Labour unelectable. Its apology needs to be profound and real. It needs to rebuild Labour as a broad church. Merit, not sect, needs to drive promotion. Labour in local government – where more is being done with less resource – needs to be an emblem of what Labour can do. And the policy agenda needs to show flexibility not rigidity. Public ownership has its place in a mixed economy. But if nationalisation is the single transferable answer to every economic problem, no one will believe it.

I am convinced that Brexit is the biggest foreign policy disaster since appeasement in the 1930s. But if Brexit is even half as bad as I think it will be, then the choices at the next election – about priorities, about tax and spending, about the sustenance of the UK, about the relationship with the EU – will be even harder than at this one. The overriding task for a new Labour leadership is to show that it has the imagination and competence to address them, free of the dogma that doomed the party in 2019.

Angry? Worried? You bet. I am currently the most recent Labour foreign secretary. I don’t want to be the last Labour foreign secretary.