Liz Truss launched an attack on British workers - saying they need "more graft" if Britain is to grow.
In a leaked recording, published by the Guardian, Ms Truss suggested Brits lacked the "skill and application" of workers from other countries, including China.
She also suggested there was a difference in effort between workers in London and the rest of the country.
Labour blasted the Tory leadership frontrunner, saying her comments were "grossly offensive" and amounted to calling Brits "lazy."
Liz Truss refused to withdraw her "more graft" comments tonight. She told a Tory hustings: “I don't know what you're quoting there.
"But the point I've always made is what we need in this country is more productivity across the country and we need more economic growth.”
The recording was made while Ms Truss was Chief Secretary to the Treasury, a post she held between 2017 and 2019.
But Ms Truss has previously faced anger over comments in Britannia Unchained, a book she co-authored with four other Tory MPs in 2012, in which British workers were derided as "the worst idlers in the world”.
Shadow Work and Pensions Secretary Jonathan Ashworth said: “With wages shrinking thanks to Tory failure to bring inflation under control and years of lacklustre growth, it’s grossly offensive for Liz Truss to effectively brand British workers lazy.
“I would have hoped she had moved on from the days of her Britannia Unchained fiasco, but it seems that is the blueprint for her prospective government.
"Workers across the country are working all hours to keep a roof over their heads, put food on the table and provide for their families.
"Liz Truss should be helping working people to cope with this cost of living crises, as Labour this week outlined we would do, not peddling this offensive nonsense.”
In the recording, Ms Truss said: “I once wrote a book about this which got mischaracterised – British workers produce less per hour than … and that’s a combination of kind of skill and application.”
She went on: "If you look at productivity, it’s very, very different in London from the rest of the country. But basically … this has been a historical fact for decades.
"Essentially it’s partly a mindset and attitude thing, I think. It’s working culture, basically. If you go to China it’s quite different, I can assure you.”
She added: “There’s a fundamental issue of British working culture. Essentially, if we’re going to be a richer country and a more prosperous country, that needs to change. But I don’t think people are that keen to change that.
“There’s a slight thing in Britain about wanting the easy answers. That’s my reflection on the election and what’s gone before it, and the referendum – we say it’s all Europe that’s causing these huge problems … it’s all these migrants causing these problems. But actually what needs to happen is more … more graft. It’s not a popular message.”
A Truss campaign source said: “These half-a-decade-old comments lack context but one thing that is as clear today as ever before is a need to boost productivity, which leads to higher wages and a better quality of life for workers right across the UK. As prime minister, Liz will deliver an economy that is high wage, high growth and low tax.”
