Opponents of Brexit are “relentlessly wanting to talk down our country”, Business and Trade Secretary Kemi Badenoch will claim.

She will warn that the benefits of Brexit risk being lost if Sir Keir Starmer gets into government, claiming the Labour leader does not believe in the “UK’s ability to think for itself”.

In her speech to the Conservative Party conference, she will acknowledge Brexit has posed “challenges” but will insist “we are working to fix them”.

But she will claim that all major economies are facing disruption to supply chains and labour problems caused by ageing demographics.

“It is only when I am back in the UK that l am told that all these issues are down to Brexit,” she will say.

“Our political opponents are obsessed with viewing every problem as Brexit. Relentlessly wanting to talk down our country.”

The Office for Budget Responsibility has forecast that leaving the European Union will lead to productivity being 4% lower in the long run than if the UK had not broken away from Brussels.

But Ms Badenoch will tell activists in Manchester that critics are wrongly claiming Brexit is “costing Britain 4% of gross domestic product per year”, saying that was not only wrong but “economically illiterate”.

She will also highlight an economic recovery from the pandemic which “outpaced France and Germany” and had seen the UK go from the world’s sixth to fifth largest exporter of goods and services.

In the City of London, “far from losing jobs”, they are at a record high, with 8% more than in 2019.

“But I’m not here to tell you that leaving the EU was without challenges,” she will say.

“That would not be true. People knew it would take time and there would be challenges along the way. What is true is that we are working to fix them.”

She will say: “We must acknowledge what we might lose if we assume the arguments are won forever.

“The people who tell you that Brexit is the cause of every problem do so because they think the answer to everything is the EU.

“Listen to what Keir Starmer says… His answer to the global challenges we face is to tax more, regulate more and ask the EU what to do next.

“This is not someone who believes in the UK’s ability to think for itself.”

She will also praise Rishi Sunak for his changes to net zero policies, telling Tory members: “We can’t deliver our targets with magical thinking, expecting those who can least afford it, to not have cars or heat their homes.

“We are on your side. The side of hard-working people, and entrepreneurs who take risks with their money and livelihoods to provide jobs and services for others.”