Britain’s high street retailers will carry the “weight of tax rises” announced in the budget, which will benefit “the least affluent” consumers, according to the chief executive of Primark’s parent company.

George Weston, the chief executive of Associated British Foods (ABF), which owns Primark as well as food and sugar brands, said the business was preparing for a big rise in costs, after Rachel Reeves’s tax-raising measures, including an increase in employers’ national insurance contributions from next April.

Weston said the change meant ABF’s national insurance bill would “go up by tens of millions” of pounds, adding: “We undoubtedly have significant increases in costs that we are facing. It is not a surprise, the money had to come from somewhere.”

Weston added: “It’s quite clear to me that this a budget where the weight of the tax rises are falling on business – within that, it’s fallen particularly on the high street.”

However, he insisted that Primark had “no intention” of raising prices during the rest of the year.

Weston also said that the budget was positive for hard-pressed shoppers, despite the hit to retailers. He said there was “actually … more good news for the least affluent in the budget than bad”.

Primark posted £1.1bn in operating profits for the year to 14 September, up 53% from the previous year.

Sales grew by 6% overall but just 1% in the UK, its largest market, as cold, wet weather in April and June hit demand for summer clothes and shoes, as well as beachwear. However, its collaboration ranges, including Rita Ora and Paula Echevarría, were popular.

Growth in UK retail sales slumped in October as shoppers put off spending in anticipation of Black Friday promotions and because of a later school half-term break in England, according to the British Retail Consortium.

Weston said a notable trend over the last two years amid the cost of living crisis had been that “people buy clothes just as they need them” rather than in advance. “They’re trying to conserve their cash from one month to the next.”

However, Weston said ABF was hopeful that wage growth, along with a budget that Reeves said met the government’s promise not to increase taxes for working people, would underpin consumer spending going in to the Christmas season.

“I hope with the budget behind us, that removes uncertainty and people have a little bit more money in their pockets,” Weston said. He added that, “if the least affluent have more income, we will benefit disproportionately”, as Primark is a budget retailer.

He also said the company was still facing pressure across its supply chain, amid ongoing disruption to trade routes along the Red Sea and anti-government protests in Bangladesh.