Rachel Reeves will pledge on Tuesday to lead the most “pro-growth” Treasury in UK history if Labour wins the general election.

Addressing business leaders, the shadow chancellor is poised to claim her party would “return to the centre ground of politics” by striking a balance between workers’ needs and business interests.

She is also expected to say she is committed to delivering economic stability so that “families and businesses can plan for the future” without the risk of “a repeat of the mini-budget”.

Labour will instead “offer a government that is pro-worker and pro-business, in the knowledge that each depends upon the success of the other”.

In a swipe at Rishi Sunak, Reeves will say the timing of the snap election was a damning indictment of his economic plans: “If he really believed his plan was working, he wouldn’t have called an election now.”

She is expected to tell business chiefs: “The general election in five weeks’ time is a chance for the British people to pass judgment on 14 years of economic chaos and decline under the Conservatives.

“Fourteen years of chaos that have seen taxes reach a 70-year high. National debt more than double. And the average mortgage holder having to pay £240 more a month after Liz Truss’s disastrous mini-budget.”

Her words will strike the same tone as the Labour party leader, Keir Starmer, who said that claims from Sunak that the UK has turned the corner were “a form of disrespect in itself”.

On Monday evening it was also reported that 121 business leaders have leant their support to Labour in a joint letter signed by former executives from JP Morgan, Heathrow, Aston Martin and JD Sports – as well as the Wikipedia founder, Sir Jimmy Wales, and Tom Kerridge, the chef and restauranteur .

“We, as leaders and investors in British business, believe it is time for a change,” said the letter to the Times, which was also signed by the founder of the childcare company that Akshata Murty, the prime minister’s wife, previously held shares and the Iceland founder Sir Malcolm Walker, who in 2015 publicly backed the Conservatives. “For too long, our economy has been beset by instability, stagnation and a lack of long-term focus.”

Reeves’s speech comes as the shadow chancellor seeks to strike a political balance between the views of businesses and trade unions. Her refusal to rule out all fire-and-rehire employment practices has drawn criticism from union leaders in recent days.

The Unite union’s secretary general, Sharon Graham, said Labour’s plans – which exclude an outright ban on the practice – had “more holes than Swiss cheese”. Reeves has since said that the plans still amount to the “biggest ever extension of workplace rights that’s ever been introduced” and that fire-and-rehire would only be tolerated in extreme circumstances such as a company going bankrupt.

She also faces further challenges in the coming weeks to illustrate how she can promise to keep a tight hand on the public finances while also rejuvenating ailing public services with fresh investment.

Reeves has promised that Labour will not oversee a “return to austerity” as she ruled out increases to income tax or national insurance.

Speaking on BBC One’s Sunday with Laura Kuenssberg, she said: “There’s not going to be a return to austerity under a Labour government. We had austerity for five years and that is part of the reason why our economy and our public services are in a mess today.”

Reeves added that the party would raise money to fund its pledges by introducing VAT on private school fees, increasing tax on private equity bonuses, extending the windfall tax on energy companies’ profits, and cracking down on non-doms and tax avoidance.