Sir Keir Starmer will use his conference speech to present himself as a serious alternative to Boris Johnson and break away from the Jeremy Corbyn era of Labour.
In perhaps the most important political speech of his career, Mr Starmer will claim “Labour will be back in business”, capable of grappling with the big issues facing the UK, including recovery from the coronavirus pandemic and tackling climate change.
Allies of the Labour leader said the speech will show how the party has changed since Mr Corbyn led it to electoral defeat in 2019.
The speech will be the biggest Mr Starmer has delivered during a leadership tenure which coincided with coronavirus restrictions that prevented him from addressing large gatherings in person.
He will highlight the fuel crisis and the rising cost of living as evidence that Mr Johnson lacks the competence required for the role of prime minister, with the government “lost in the woods”.
Mr Starmer took over from Mr Corbyn after the party suffered its worst result since 1935, when the Conservatives won a landslide victory in 2019.
In an attempt to convince voters that Labour is a credible government-in-waiting, Mr Starmer will say: “Too often in the history of this party our dream of the good society falls foul of the belief that we will not run a strong economy.
“But you don’t get one without the other.
“And under my leadership we are committed to both.
“I can promise you that under my leadership Labour will be back in business.”
A source said the speech will be “noticeably different from what you’ve heard from Labour in recent years”, adding: “It will be a clear indication that Labour will never again go into an election with a manifesto that isn’t a serious plan for government.”
The speech, which Mr Starmer began writing on a holiday in Dorset during the summer, draws on his experience of talking to voters who have deserted Labour.
The party believes that voters in Red Wall seats, who had given Mr Johnson the benefit of the doubt, were now concerned about his competence.
A Labour spokesman said: “We know the shine is coming off Boris Johnson. We know that we are in a situation where there are serious questions around the competency of the government, its ability to deliver.”
Mr Starmer's speech will present Labour as a credible opposition to a government which is “strong on slogans and weak on strategy”, the spokesman said.
“I see the government lost in the woods with two paths beckoning,” Mr Starmer will say.
“One path leads back where we came from.
“None of the lessons of Covid are heeded.
“The divisions and flaws that were brutally exposed by the pandemic all worsen.
“But there is another path down which we address the chronic problems revealed by Covid with the kindness and the togetherness that got us through.
“That path leads to a future in which a smart government enlists the brilliance of scientific invention to create an economy in which people are healthy and well-educated.
“A contribution society in which everyone has their role to play.”
The country faces big issues, including “how we make our living in a competitive world”, the future of the Union and the relationship with Europe.
“These are big issues.
“But our politics is so small,” Mr Starmer will say.
“So our politics needs to grow to meet the scale of the challenge.”
His wife, Victoria, will be in Brighton to watch the speech, which aides said would set out some of his personal background and values.
The keynote address will close a conference when Andy McDonald resigned from the shadow Cabinet and there was a bust-up with unions and the left of the party over internal rule changes.
But Mr Starmer's allies believe the rows with the Corbynite wing of the party were necessary to have now, to prepare the party for a snap general election if Mr Johnson goes to the country before the scheduled 2024 vote.
“What we will be using the speech to do is to show that these are serious times that require a serious leader, and that is Keir Starmer,” the spokesman said.
“I can promise you that under my leadership Labour will be back in business.”
