Sir Keir Starmer will warn of a “shared struggle” ahead but say there is “light at the end of the tunnel” for the country, in his first speech to the Labour Party conference as prime minister.
The PM will say “tough” decisions need to be taken now to “build a new Britain”.
Since winning power, the Labour government has painted a bleak picture of the public finances – but in his speech the PM will seek to present a more positive vision for the future.
However, he is facing anger from unions and many Labour members over the decision to cut winter fuel payments for millions of pensioners.
A row over donations to Sir Keir and other Labour ministers has also dampened the mood of the conference in Liverpool – which is taking place less than three months after the party’s landslide election victory.
In his speech, Sir Keir will promise a future of “national renewal”.
“The politics of national renewal are collective. They involve a shared struggle,” he will say.
“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.”
Echoing the message his Chancellor Rachel Reeves gave in her speech on Monday, Sir Keir will say that “if we take tough long-term decisions now” there will be “light at the end of the tunnel”.
However, he will warn against “easy answers” and offering “false hope”.
Sir Keir will also announce new legislation to crack down on welfare fraudsters, which Labour says is expected to save £1.6bn over the next five years.
Under the plans, the Department for Work and Pensions will get new powers to investigate suspected benefit fraud and recover debts from individuals who can pay money back but have avoided doing so.
Labour said there would be safeguarding measures to protect vulnerable claimants.
Elsewhere in his speech, Sir Keir will commit to reducing net migration by training Britons to fill vacancies in the jobs market rather than allowing employers to rely on overseas labour.
The prime minister will also promise to introduce a Hillsborough Law requiring a duty of candour for public officials.
It is intended to give greater powers to victims of major disasters, such as the families of the 97 Liverpool fans killed in the 1989 stadium crush and the 72 killed in the Grenfell Tower fire.
The party has accused the previous Conservative government of leaving a £22bn “black hole” of unfunded spending commitments in the public finances – something the Tories have disputed.
Sir Keir will repeat the claim in his speech, saying the Tories have also “decimated public services, leaving communities held together by little more than goodwill”.
But he will warn the pockets of working people “are not deep” and public services will need “reform” as well as investment.
“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,” he will add.
Labour has repeatedly promised it will not raise taxes on “working people”, including VAT, National Insurance and income tax.
However, the chancellor has already said she will have to raise some other taxes in October’s Budget because of the state of the public finances.
The government has also blamed the £22bn black hole for the decision to cut winter fuel payments.
A debate and non-binding vote on the issue had been expected on Monday but could now take place on Wednesday, when many activists will have left the conference.
Unite, which is among the trade unions calling for the cut to be reversed, branded the delay an “outrage”.
