NatWest was forced to spend £24m on the former Conservative government’s aborted “Tell Sid”-style campaign featuring Sir Trevor McDonald, which would have resulted in a chunk of the bank’s state-owned shares being sold to the general public in a highly anticipated privatisation drive.

The price tag emerged when the bank released its second-quarter results and announced that it was snapping up a number of mortgages from the smaller rival Metro Bank for £2.4bn.

Agreements with the government dating to the bank’s bailout in 2008 meant NatWest was on the hook for costs linked to the campaign, including advertising, printing and distributing documents, as well as legal fees and expenses.

The Tory government had already hired a fleet of advisers, including from Goldman Sachs, Barclays, the advertising house M&C Saatchi, the law firm Freshfields and the retail share sale experts Solid Solutions, to prepare the programme.

The process, which the former chancellor Jeremy Hunt announced during last year’s autumn statement, was due to launch this summer, with a big public “Tell Sid” campaign – a reference to the slogan used to encourage the public to buy shares in the newly privatised British Gas in 1986.

Hunt’s plan was part of the Tories’ efforts to return the bank – formerly known as Royal Bank of Scotland – to private ownership by 2025-26, after its £46bn taxpayer bailout during the height of the financial crisis. There were also hopes that the campaign would encourage everyday savers to start investing in British stocks.

The Guardian revealed last month that TV ads had already been filmed featuring McDonald, the veteran newsreader and presenter, popping up around the UK asking the public: “Are you in?”.

However, the campaign plans were abruptly cancelled in May after Rishi Sunak called an early general election.

The new Labour government has not confirmed whether it will pick up where the Tories left off, leaving NatWest to shoulder the cost. However, the chancellor, Rachel Reeves, is reportedly leaning towards scrapping the retail share sale to focus on selling off the remaining 19.9% stake to institutional investors, including asset managers and pension funds, according to Bloomberg.

The decision could end up being cheaper both for the government and bank, and could free up time and staff who would otherwise be dedicated to managing the programme.

Paul Thwaite, the NatWest chief executive, declined to comment on the government’s plans but told journalists that Reeves would probably give an update during the autumn statement. “The reality is that the policy for any sort of share sale is usually set out during fiscal events. Obviously, the new government hasn’t had one, but we’d expected it to follow the next fiscal event,” Thwaite said.

“But what I’d come back to is a halving of the [government’s] shares during the last six months is a really positive trajectory … Returning the bank into private hands, I believe, is in the best interest of all of our shareholders.”

The figures were released as NatWest reported earnings results showing pre-tax profits slipped 4.1% to £1.7bn over the three months to the end of June, compared with a year earlier. However, that was better than the £1.3bn than analysts had forecast.

The bank recorded a 2.4% drop in net interest income, which is a key measure of profitability for lenders, and accounts for the difference between what is charged for loans and what is paid out to savers, to £2.8bn, beating expectations of £2.6bn.

The bank had also been expected to put aside £161m for potential defaults but instead released £45m, thanks to the UK’s improving economic outlook.

It helped push NatWest shares up by as much as 9.1% at one point on Friday, hitting its highest level since February 2015.

NatWest also hoovered up 10,000 new customers through the acquisition of Metro Bank’s prime mortgage book. It is Thwaite’s second acquisition this summer, after striking a deal to buy most of Sainsbury’s Bank in June.

The Co-operative Bank released its financial results on Friday , showing a 60% drop in first-half profits to £24.2m. The bank, which is being sold by its hedge fund owners to Coventry Building Society for £780m, said the fall in profits was due to lower income in a period marked by heightened competition for fewer mortgage customers. It was also hit by higher costs linked to higher salaries, reimbursing fraud victims, and levies paid to the Bank of England.