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Boris Johnson’s promise to hire 50,000 more nurses was twice as important as Brexit in wooing former Labour voters in the so-called red wall seats, a new inquest into the party’s election defeat has found.

The fresh study into why Jeremy Corbyn lost in 2019 found that – just like the 2016 referendum pledge of £350m a week for the NHS – Tory pledges on nurses and 50 new hospitals resonated with traditional working class voters in the north of England and midlands.

The analysis, by campaign group Labour for a European Future and shared exclusively with HuffPost UK, argues that Keir Starmer can only win the next election if he persuades the party’s former voters he has a stronger offer than Johnson on health, jobs and crime.

And with the Covid-19 crisis highlighting the importance of public health cuts, Labour has to come up with memorable and specific policies to show it has learned the lessons of the pandemic better than the Tories, it suggests.

The new ‘Lessons For Labour’ study makes clear that unhappiness with Corbyn’s leadership and his lack of credibility on policy was the main factor overall in Labour’s shattering defeat to a Tory majority of 80 last December.

But it also singles out the NHS as a Tory secret weapon among ex-Labour voters, highlighting a YouGov finding that Johnson’s 50,000 more nurses promise was the most popular policy the firm had ever polled.

The report picks up on a finding buried in a megapoll by Tory peer Lord Ashcroft, showing that Leave voters who had backed Labour in 2017 had very different motivations from Leave voters who backed the Tories.

A huge 68% of Labour Leavers said the NHS was the main driver for them voting Conservative in 2019, more than twice the number (29%) who said “getting Brexit done” was the biggest reason. In contrast, 76% of Tories gave Brexit as their prime motivator.

Report co-author Mike Buckley said: “It’s a mistake to think that thousands of people voted Conservative for the first time just to get Brexit done. Labour-Tory defectors were far more motivated by Johnson’s promises on nurses, police officers and hospitals.

“Those policies were not plucked out of thin air – they were targeted at people who have seen public services decline for years and want better. For Labour to win voters back it needs a credible and specific offer on health and crime.”

The report itself states: “Labour Leave voters are not the same as Tory Leave voters. Their priorities are different. Had Labour offered Labour Leavers a policy programme more appealing to them, and leadership they could believe in, more could have been retained.”

Even though the 50,000 “new” nurses claim was heavily criticised for relying on retaining current staff, it was repeated so often that the Tory message got through, the report’s authors say.

Labour’s main NHS campaign issue in the election centred on disputed claims that the Tories would try to sell off the health service to America in a trade deal.

Its own shadow health secretary Jonathan Ashworth has since admitted there was not enough focus on policies to improve the NHS or attack Tory waiting lists and shortages.

“Labour must be specific about the NHS. ’24 hours to save the NHS’ leaflets don’t work because voters don’t believe it is in danger. We have to answer the question of how the NHS would be better under Labour,” the report says.

“Labour must make the case for public health. Post-virus it will be even more important. It has been underfunded by the Tories.”

More broadly, the report says that voters want credible policies combined with credible leadership.

“They will not turn out for socialist utopia, which has never been a preoccupation of the majority. They will turn out for things that they believe will make a real difference to their lives.

“Blair’s pledge card in 1997 promised real, measurable change to class sizes, NHS waiting times, getting young people into work, dealing with young offenders and a strong economy. Labour must speak to voters’ priorities, and not expect that they will come behind ours.”

The post-mortem does however stress that Labour lost as many Remain voters as Leave voters in 2019 – 1.1 million of each – and blames the party’s lack of clarity over a second referendum and whether it would campaign to stay in the EU.

It also says that no election can be won without an increase in Labour seats in Scotland, where close links with the EU are especially popular.

A new MRP poll for the Best for Britain campaign found that even in ‘Red Wall’ seats, 90% of voters felt that getting a trade deal with the EU was either “important” or “very important:” some 60% of Labour-to-Tory switchers worried that prices would rise without a deal.

Another survey by IpsosMORI found that 70% Leave voters aged under 48 think the UK should actually keep or increase EU regulations and standards.

“Brexit is not done. Voters still care about our relationship with Europe – and will continue to do so. Labour needs to make the case for a close relationship with Europe as the best outcome for the NHS, jobs, wages and security,” the election report says.

“Labour cannot ignore the issue of Europe. It is deeply important to many people. Labour will need a clear position on our economic, trade and security links with the EU in 2024.”

The report is withering too about the repeated failure of the past three Labour leaders to connect with voters, ridiculing the claim from some Corbyn supporters that they “won the argument”

It says that in 2010 “we lost the argument over the crash”, in 2015 “we lost the argument over austerity” and in 2020 “we lost the argument over Europe” and credibility.