Sir Keir Starmer has denied Labour will be breaking promises to voters by hiking employer national insurance contributions.

The Prime Minister claimed his party’s manifesto specifically referred to “working people”, as the Government looks set introduce a so-called jobs tax to claw in more money.

Critics have warned the move will hammer business confidence and scare away investors.

Asked whether the Labour manifesto ruled out any increase in National Insurance, the Prime Minister said: “We were very clear in the manifesto that we wouldn’t be increasing tax on working people.

“And we expressly said that that was income tax, that was NICs, etc.”

Pressed on whether this included employer contributions, Sir Keir added: “It’s very clear from the manifesto that what we were saying is we’re not going to raise tax for working people, and it wasn’t just the manifesto.

“We said it repeatedly in the campaign, and we intend to keep the promises that we made in our manifesto.

“I’m not going to reveal to you the details of the budget.

“You know that that’s not possible at this stage. What I will say is, where we made promises in our manifesto, we will be keeping those promises.

“This is going to be a manifesto that is going to be tough. It’s going to be a budget that’s going to be tough, of course.

“But the focus will be on rebuilding our country, and ensuring that we get the growth we need in our economy and so it’s consistent with the summit we had yesterday.

“And this money that is now coming in which will be a real game changer for our country.”

Chancellor Rachel Reeves gave her strongest signal yet employer national insurance contributions will be hiked to raise billions of pounds in her maiden Budget on Oct 30.

Ms Reeves insisted bosses “get” that she must increase tax receipts to balance the books.

Tory MP Neil O’Brien added: “Not that long ago Rachel Reeves was slating the idea of increasing employers national insurance as a “jobs tax” which would ultimately just come out of the pockets of normal people, and the Office for Budget Responsibility agrees that the cost will just be passed onto workers anyway.

“Combined with Labour plans to borrow and spend more and other plans they are threatening, lots of this will already be putting off people from investing in the UK”.

Laura Trott, Shadow Chief Secretary to the Treasury said: “The Chancellor has chosen Labour’s first investment summit to sow further uncertainty and chaos for businesses who are now braced for Labour’s Jobs Tax.

“Regardless of what they say, it’s obvious to all that hiking employer National Insurance is a clear breach of Labour’s manifesto. Rachel Reeves herself previously called it anti-business and we agree, it is a tax on work that will deter investment, employment and growth, and the OBR says it will lower wages.”

But the Chancellor said: “Businesses want two things. They want a competitive tax system and competitive regulation and planning and all the rest of it.

“If we come out of that Budget and there’s not a serious plan to balance day to day spending through tax receipts, get debt down as a share of GDP, I’m afraid businesses will continue to look at Britain and say we’re not serious.

“So, I don’t regard it as a sort of dilemma between returning the economy to a path of stability on the one hand and attracting investment on the other.

“Unless you put Britain on a stable economic and financial path, we’re not going to be able to get that investment in.

“That will mean some difficult decisions, including on taxation.

“Businesses get that. They know that we’ve got to be able to pay for day to day spending through tax receipts.”

The Chancellor admitted the upcoming Budget will be “tough” and there will be a “difficult balancing act”.

She said: “I don’t think it’s any surprise to the British people that the first Budget of this new Labour Government is going to be tough – to get public services back on a firm footing, to get our public finances on a stable path, whilst also trying to ensure that working people are not going to be paying more and more of their hard earned money in taxes.

“So it’s a difficult balancing act. But I think the public understand the scale of the challenge that we are facing.

“We were really clear in our manifesto that we weren’t going to increase the key taxes paid by working people – income tax, national insurance and VAT.

“And on the business side, our commitment that we would cap corporation at 25%, which is the lowest in the G7, and we will stick to the commitments we made in our manifesto.

“But you know that there’s a £22bn black hole over and above anything that we knew going into the election.

“The precondition for bringing investment into a country is economic and fiscal stability.

“So we are going to need to close that gap on what the Government is spending and what we’re bringing in through tax receipts.

“Decisions will need to be made.”

Prime Minister Sir Keir Starmer on Monday confirmed an additional £63 billion will be invested in the UK economy.

This includes an extra £1.1bn boost to Stansted, expanding the existing terminal by a third, opening up new routes to holiday destinations across Europe.

Construction is expected to begin early next year.

Spanish energy company Iberdrola also confirmed it will double its £12bn investment to £24bn, with £4bn set to be spent on a huge wind farm off the Suffolk coast

Sir Keir said in a speech to the International Investment Summit, that it was “an age of great possibility” with a “huge revolution in digital technology, in clean energy, medicine, life sciences, each with a competitive potential to fundamentally change the way we live and the way that we work”.

The summit, at the Guildhall in the City of London, was compered by Bridgerton star Adjoa Andoh, with guests invited to an exclusive reception at St Paul’s Cathedral, attended by the King and featuring a performance from Sir Elton John.

After a bruising few weeks of headlines dominated by turmoil in Number 10 and a row over freebies given to Cabinet ministers, Sir Keir promised to “think in years” rather than “the days or hours of the news grid”.

In his keynote speech he said: “We’ve got our problems, of course we have. As I’ve said, our public services need urgent care, our public finances need the tough love of prudence – challenges we can’t ignore.

“Because we know, just as every leader here knows, that those early weeks and months are precious, and no matter how many people advise you to ignore it, that you must run towards the fire to put it out, not let it spread further.”

With Rachel Reeves’ first Budget on October 30 and the prospect of tax rises to help repair the public finances, Sir Keir stressed the importance of growth in providing extra cash for the Government.

It marks a change in tone after the Government had faced criticism for being too gloomy about the state of the economy and public finances.

The Prime Minister said growth was “the only way to deliver the mandate for change we won” at the general election.

“Growth is higher wages. Growth is a more vibrant high street. Growth is public services back on their feet, it’s less poverty, more opportunity, more meals out, more holidays, more precious moments with your family, more cash in your pocket.

“And, of course, for any business it means a bigger market, higher demand, a more secure and prosperous future.”

Sir Keir said it is “time to upgrade the regulatory regime” as he pledged to “rip up” bureaucracy holding back investment.

He said the Government will “make sure that every regulator” in the country takes growth “as seriously” as businesses.