Ed Davey is to pledge a £5bn-a-year guarantee of free care packages for all in England as the Liberal Democrats gather for their first in-person conference since 2019. Desperate to translate recent byelection successes into a mass haul of parliamentary seats, the Lib Dem leader plans to use the event in Bournemouth, which starts on Saturday, to become the first of the major UK political parties to set out a suite of specific policy ideas. With the election due next year, delegates will debate and vote on a 50-page “pre-manifesto” setting out a series of promises, some more general but others, like the care pledge, notably specific. Speaking to the Guardian before the conference, which follows the cancellation of the 2020 and 2021 events due to Covid and last year’s because it clashed with Queen Elizabeth II’s funeral, Davey said a plan for care was all the more vital after Theresa May and Boris Johnson reneged on promises to reform the creaking sector. The idea is to mimic the policy in Scotland, where what is known as personal care – the attentions of a carer, either at home or in a care setting – are free, which Davey said would allow many more people to return home quickly from hospital, freeing up beds. While the upfront costs to roll this out in England would be about £5bn a year, Davey said the savings to the NHS would claw back at least £3bn of this. “It’s a lot less expensive than people in the Treasury fear, and it’s a policy whose time has come,” said Davey, who is a carer for his son John, who is disabled. “It would transform the lives of millions of family carers, it would rejuvenate the care sector, and it would be a massive win for the health service,” he said. The pre-manifesto also lists some existing Lib Dem policies, such as a proposed higher minimum wage for carers and significant spending on eco-retrofits for homes, while managing to not mention Brexit once, merely pledging to improve links with Europe. The slightly cautious approach is in sharp contrast to the last time the Lib Dems held an autumn conference, also in Bournemouth, when the then leader, Jo Swinson, promised to reverse Brexit without a referendum if the party somehow won a Commons majority, while one then MP briefed journalists that they could win between 100 and 200 seats. The eventual tally was 11, with Swinson among the Lib Dem losses. Davey took over, initially as interim leader, and has guided the party to a series of stunning byelection wins against the Conservatives – they now have 15 MPs – starting with overturning a 16,000 majority in the commuter belt seat of Chesham and Amersham in June 2021. This saw the emergence of the idea of the “blue wall” – formerly safe Tory seats, often in relatively affluent areas, where more liberal-minded Conservatives have grown disenchanted with the more populist approach of Boris Johnson and Liz Truss. Davey argued that Rishi Sunak had proved little more appealing, especially now he has moved to the right in areas such as migration and net zero. “You had Johnson, who was just dishonest – I don’t think that’s contested,” he said. “You then had the chaos of Truss. And now you’ve got the carelessness of Sunak. I’ve never really looked at a prime minister of our country and thought: you just don’t get what it’s like for people. And that’s the sense you get from Sunak.” With byelection gains also in the party’s former heartland of the south-west of England, Davey is notably bullish about his party’s prospects for the next election, while stressing he is “resolutely not putting numbers on it”. “There are more seats in the blue wall for taking than I had expected,” he said. “In the blue wall it’s seats we actually weren’t contesting in the 1990s. And then we have some of our old battlegrounds. “I’m not going to talk numbers, but it is fair to say we’re optimistic that in these sorts of areas, people are switching to the Liberal Democrats, because they know we can beat the Conservatives.” As an election looms, Davey said he felt “a heavy responsibility” over his party’s potentially pivotal role in removing the Conservatives from power by winning in areas where Labour cannot. “We are looking at millions of people struggling. We’re looking at the NHS in absolute crisis, the care system in absolute crisis, I’ve never known it so bad,” he said. “And so we have to get them out, we absolutely have to. I said when I became leader that my job is to defeat as many Conservative MPs as possible. I think that remains the task.”