Sir Keir Starmer will defend focusing on “short-term pain” for “long-term gain” as he reiterates the need for “tough decisions” during his keynote speech at the Labour Party conference.

Speaking in Liverpool on Tuesday, the prime minister will again point to the £22bn “black hole” in public finances he claims was left by the Conservatives, saying there are “no easy answers” to fixing it, and refusing to offer “false hope” to the public.

But he will promise to “build a Britain that belongs to you” and “once again serves the interests of working people”, adding Labour’s plan will ensure the country “gets there much more quickly”.

Sir Keir is also expected to pledge a cut in net migration by increasing training opportunities in the UK, rather than “importing labour” from abroad, and a crackdown on benefit fraud, as well as tackling long-term sickness “to get people back to work”.

And he will commit to introducing a “Hillsborough Law”, named after the 1989 football stadium tragedy which resulted in the deaths of 97 people, by its next anniversary, which would introduce a statutory duty of candour on public servants during all forms of public inquiry and criminal investigation.

Having promised the legislation if Labour won power at its party conference two years ago, the prime minister will say it is “a law for Liverpool, a law for the 97, a law that people should never have needed to fight so hard to get – but that will be delivered by this Labour government”.

Ministers have come in for criticism in recent weeks for their gloomy approach to the state of the economy and public services, already warning there will be a “painful” budget at the end of October to balance the books.

But during its annual conference, being held in Liverpool this year, the government has sought to inject some optimism into its outlook, rejecting a return to “austerity” and claiming to have “real ambition” for the future of the UK.

Taking a similar approach, Sir Keir will tell the gathered politicians and activists during his first conference speech as prime minister: “The politics of national renewal are collective. They involve a shared struggle.

“A project that says, to everyone, this will be tough in the short-term, but in the long-term, it’s the right thing to do for our country. And we all benefit from that.”

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Chancellor: ‘No return to austerity’

Citing his missions for government, including raising living standards through higher economic growth, cutting waiting lists in the NHS, and making streets safer, he will say: “The truth is that if we take tough long-term decisions now, if we stick to the driving purpose behind everything we do… then that light at the end of this tunnel, that Britain that belongs to you, we get there much more quickly.”

But, Sir Keir will add: “It will be hard. That’s not rhetoric, it’s reality.

“It’s not just that financial black hole, the £22bn of unfunded spending commitments, concealed from our country by the Tories, it’s not just the societal black hole – our decimated public services leaving communities held together by little more than goodwill – it’s also the political black hole.

“Just because we all want low taxes and good public services, does not mean that the iron law of properly funding policies can be ignored.

“We have seen the damage that does, and I will not let that happen again. I will not let Tory economic recklessness hold back the working people of this country.”

However, Conservative Party chairman Richard Fuller hit back, saying: “Labour have only been in office for 81 days, but so far they have already shown the only interests they are serving are their own.

“From picking the pockets of pensioners to fund their union paymasters’ pay-rises, to their litany of ex-Labour staffer appointments in the civil service, Starmer’s government are clearly putting themselves first, the Labour Party second, and the country last.

“Rather than seeking national renewal, Starmer’s political decisions risk running the country into the ground.”