Keir Starmer has promised there will be "no magic money tree economics" if Labour gets to power in a dig at the Tory leadership candidates.
The Labour leader hit out at Rishi Sunak and Liz Truss's "Thatcherite cosplay" as he promised to pursue "growth, growth, growth" and that under his party the economy would be "strong, secure and fair".
He vowed a Labour Government would be "financially responsible" as he attacked the "Conservative competition to waste more of your money".
"In one corner you have Rishi Sunak, the architect of the cost-of-living crisis," Mr Starmer told an audience in Liverpool.
"In the other you have Liz Truss, the latest graduate from the school of magic money tree economics.
"Neither of them has the answers to the economic challenges that we face."
As Tory hopefuls "rage against the dying of the Thatcherite light", it's clear they "don't understand" what's needed to fix the economy, he said.
It comes as the rivals to take over from Boris Johnson as Prime Minister have been engaged in a bitter race to win over Tory members by claiming the mantle of Margaret Thatcher.
Ms Truss has said she would borrow more to fund tax cuts, even though interest rates could be pushed up, while Mr Sunak says he would take a more cautious fiscal approach.
But in a speech in Liverpool, Mr Starmer vowed that "growth, growth, growth" to pull Britain out of economic decline will be the next Labour government's priority.
He channeled Tony Blair's "education, education, education" mantra to underline that growth will be his immediate focus if he makes it to No10.
It represents a shift away from Labour's previous focus on redistribution and investment as the main tools to bolster the economy.
"The approach to growth I have set out today will challenge my party's instincts," he said.
"It pushes us to care as much about growth and productivity, as we have done about redistribution and investment in the past.
"Not to hark back to our old ideas in the face of new challenges".
He said he was concerned people from his "working class" background cannot get on, and asked: "What does it say about the state of Britain when working people feel hard work doesn't pay?"
Mr Starmer also revealed plans for an Industrial Strategy Council, on statutory footing, which would hold his Government to account over decisions it makes.
And he condemned the Tory government's record over the last decade.
"Whether it's the cost of living or recovering from the pandemic, our economy is weaker than its competitors. Less resilient. Brittle. And ultimately, we are all poorer for it," he said.
"With me and with [shadow chancellor] Rachel Reeves, you will always get sound finances; careful spending; strong, secure and fair growth.
"There will be no magic money tree economics with us."
Mr Starmer also hit back at any suggestion that economic growth and the UK's push for net-zero are incompatible.
"We will not be distracted by the siren calls - from the right or the left - that say economic growth and net-zero do not go together," he said.
"A plan for net zero needs growth; a plan for growth needs net zero. Fail to tackle climate change and you can forget about growth.
"Some nation is going to lead the world in electric vehicles, in floating offshore wind, in new hydrogen and technological development. Why not Britain?
"The growth I want for Britain is strong, secure and fair."
The Tory leadership candidates have been lukewarm about their commitments to tackle climate change.
It comes after Shadow Chancellor Rachel Reeves said that Labour could pledge tax cuts for millions at the 2024 election.
She told the Mirror workers should “keep more of their money” - funded by a possible hike on those who profit from stocks, shares and dividends.
