Who’s afraid of the Beckett report into Labour’s disastrous defeat last May? Not me, and nor should anybody on the left. We should be consumed – obsessed even – by research into Labour’s loss. The left is sometimes, wrongly, caricatured as more concerned with purity than power, all about grandstanding and posturing, happy to sacrifice the interests of those for whom Labour was founded as its principles give it a warm glow.

Principles v power is a false dichotomy, of course. What is the point of a vision unless you can convince enough people to support it and transform the country? The left’s central mission must be a route to power, but that doesn’t mean having to accept the underlying principles of its opponents. Putting on a blindfold may help us ignore obstacles for a time, but it will not prevent the inevitable collision.

I haven’t read the report – few have yet – but the leaked conclusions should be of no surprise. First, we didn’t need a report to establish that “a failure to shake off the myth that the last Labour government was responsible for crashing the economy” was a critical factor in its defeat. This, above all else, explains why Labour badly lagged behind the Tories on economic credibility, however parlous a state the economy was in and however anaemic the growth. Both the Labour leadership and the Labour right – ironically, those who accused the left of trashing New Labour’s record – refused to seriously challenge the myth that overspending by Tony Blair and Gordon Brown caused the crash. It was Blair and Brown’s leftwing critics who were loudest at refuting this lie: and at highlighting the fact that George Osborne backed every single penny of Labour’s spending. Without refutation, the Tory attack line of “why hand the keys back to the driver who crashed the car” proved a phenomenal success.

Labour has to find a story that has an emotional connection

Second, Labour failed to convince on immigration and social security. Polling on both issues may be discomfiting, but it is conclusive. Most people think there is too much immigration, and believe that social security spending lines the pockets of the feckless. Such widespread attitudes are self-evidently propitious for the political right. Labour will not win the argument by singing the praises of immigration and social security alone, or by bombarding the electorate with statistics that don’t resonate. Labour has to find a story that has an emotional connection. On immigration, it should contemplate policies such as an immigration dividend that means the economic benefits are spent in communities with higher rates of newcomers.

Third, there was “a fear among voters of the SNP propping up a minority Labour government”. One senior Unite official told me of a branch full of lifelong trade unionists and Labour supporters: “we can’t let the Scots run the country” was the mood. The Tories and their allies very successfully whipped up anti-SNP resentment and English nationalism, combined with a sense that Labour had a weak leader who would be held over a barrel by a strong SNP committed to “breaking up the country”. How can such an onslaught be countered? Labour has to think hard, and now.

Finally: Ed Miliband was rejected as a potential prime minister. Whether Jeremy Corbyn remains for the long haul, or proves a transitional figure who makes way for somebody else, leadership matters. Allowing a hostile media to shred a leader to pieces by writing off presentation as New Labour-type spin would be a fatal mistake.

The report also apparently emphasises that policies associated with the “left” – such as public ownership of rail or an energy freeze – were among the most popular, but there was a lack of a coherent narrative. You can say that again. Throwing random policies into the ether is a waste of time, and will leave the public (at best) bewildered. In the Miliband era, Labour jumped restlessly from message to message – from the “squeezed middle” to the “promise of Britain”; “one-nation Labour”; “predistribution”; and so on. The Tories have a clear narrative backed up by endlessly repeated messages. A series of populist policies is no guarantee of victory: there needs to be a compelling overall story.

I could add many other ideas. “Socialism is the language of priorities,” said Nye Bevan: Labour has to focus on policies that resonate with people’s everyday lives, rather than picking fights on contentious but peripheral issues. Socialism means building a society run in the interests of the majority: that means those in the middle, as well as the poorest. The Tories only had a lead among the over-44s: Labour needs an inspiring message for older Britons, not least because we have an ageing society. There will soon be more self-employed people than public-sector workers – what’s Labour’s message for them.

Publish away. Let’s have a full inquest, not in the interests of navel-gazing, but in the interests of winning. Every time the Tories win, the political centre of gravity shifts to the right. Millions pay the price. Unacceptable. The left can win, and we must show how.