But other economists have expressed scepticism about the claims, pointing to HMRC modelling which shows raising capital gains would lead to a big drop in revenues as many owners would choose to hold on to their assets rather than sell.
Estimates produced by the taxman show that increasing the top level of capital gains by 10 per cent to 34 per cent, still shy of the 40 per cent higher-rate income tax band, would cost the Treasury £3.6bn a year by the end of the decade.
Rachel Reeves, the Chancellor, has already announced the scrapping of the Energy Company Obligation, which added the cost of insulation grants to bills, and reduced the Renewables Obligation, which subsidises wind and solar farms, by 75 per cent for the next three years. The move is estimated to save households £150 on their bills.
If Mr Burnham pushes ahead with further cuts to green levies as prime minister, it would bring the combined cost savings of both interventions to £280 a year for households.
Sir Mel Stride, the shadow chancellor, said: “We should be backing investment and wealth creation in this country. A huge increase in capital gains tax would be a disaster for investment.
“Andy Burnham needs to rule this out urgently before speculation sees people selling up.”
Shadow minister Katie Lam said: “We’re in this mess because of Labour’s obsession with taking money from people who work hard, to spend more money on those who don’t work at all. Burnham wants to double down, and is attacking those who take risks, build businesses and create jobs.
“His plans would drive jobs out of Britain, crush businesses and make us all poorer. It’s a wealth tax by stealth, straight out of the Zack Polanski playbook.”
In a separate report published on Thursday by ThinkLabour, Mr Burnham was urged to increase income tax and scrap the pensions triple lock.
In what would be a breach of Labour’s manifesto commitments, the think tank argues that Labour should raise the basic rate of income tax by 1p and water down uplifts to the state pension. The reforms would raise £10bn.
ThinkLabour, formerly Labour Together, was previously run by Josh Simons, the former Makerfield MP who quit his job to pave the way for Mr Burnham to run as a Labour candidate, and is now helping draw up policy for his team.
It has been widely speculated that Mr Burnham, who was sworn in as an MP earlier this week and widely predicted to be Sir Keir Starmer’s successor, is said to back scrapping the triple lock, although his team has ruled out an increase in income tax.
