“How are you going to pay for it?” Over the past 14 years, it would seem that no other question has been so destructive for British society. That is because the vast majority of the country’s leading politicians still seem to believe that additional public spending or investment is impossible to finance. The result is a belief, explicitly stated or not, in the need for continued austerity, which is the policy that has seriously undermined UK economic performance since 2010.

It was when Labour’s shadow leader of the House of Commons, Lucy Powell MP, said that there was “no money left” in July 2023 – echoing Liam Byrne’s infamous note to his successor in 2010 – that I thought it was time to show she was wrong about this. The Taxing Wealth Report 2024 is the result.

In the report, I show that by making up to 30 relatively simple changes to existing UK taxes, and to the way our tax system is managed, up to £90bn of new tax revenue could be raised a year. These sums would come almost entirely from those in the top 10% of income and wealth holders in the UK, or from those who live off unearned income such as dividends, rents, interest and capital gains.

Tuesday’s pledge by Rachel Reeves to increase funding to HMRC to close the “tax gap” – the difference between the amount the British state is owed and receives – is welcome. But it does not either go nearly far enough, or change anything about Labour’s fundamental approach to the economy.

My focus on those with wealth – as opposed to those who depend on their labour to get by – is not by chance. These groups are seriously undertaxed in the UK at present. Looking at the average tax paid on the combined average income, and increases in wealth of all groups in society for the years 2010 to 2020, those on the lowest incomes paid tax at average rates of up to 44% of their income, while those at the top of the income range paid tax at little more than 20%, on average. The prime minister, Rishi Sunak, paid approximately 23% tax on his earnings of more than £2m in the tax year 2022-23.

Here are some policy ideas that could be implemented:

1) Charging capital gains to tax at the same rate as income tax might raise £12bn of extra tax a year.

If this policy had been in operation in 2022-23, Sunak would have paid £808,200 on the £1.8m of investment income he made that year because his tax rate on those gains would have increased from 20% to 45%.

2) Charging VAT on the supply of financial services, which are inevitably consumed by the best off, could raise £8.7bn of extra tax a year.

These charges would mainly apply to the fees of banks, financial advisers, pension consultants and mortgage advisers, most of whose charges do not carry VAT at present.

3) Charging an investment income surcharge of 15% on income from interest, dividends, rents, capital gains and other such sources might raise £18bn of extra tax a year. Lower rates could, of course, be charged and annual tax-free allowances could be given.

4) Charging national insurance (NI) at the same rate on all earned income, whatever its amount above the statutory minimum, might raise up to £10bn of extra tax a year.

This change would remove the anomaly that while NI is charged at 8% on earnings between £12,570 and £50,270 a year, the rate on earnings above £50,270 is reduced to 2%. So a person earning £60,270 a year would under this proposal owe an additional £600 of NI a year. However, my report does suggest that their income tax rate should be cut from 40% to 30% on earnings between £50,270 and £75,270, so this person would overall be better off by £400 compared with now.

5) Investing £1bn in HMRC so that it might collect all tax owing by the UK’s 5m or so companies, when 30% of that sum goes unpaid at present, might raise £12bn a year.

The £1bn – which represents about 20% of the current yearly total running costs of HMRC – would permit the reopening of local tax offices throughout the UK where local tax inspectors (of the sort that existed until 10 to 15 years ago) could be employed to track down the local companies that do not pay tax, not least by turning up on their premises and asking to inspect the records and then collect the tax due. That worked in the past. It could do so again. Rachel Reeves’s plan to spend about half this sum does not go far enough and must be focused in the right places: the big tax losses are not offshore now but are, instead, in the domestic economy, which is why local tax offices, staffed by people with local knowledge, are needed.

One more revenue-raising measure: if the tax incentives for saving in ISAs and pensions were changed so that all new ISA funds and 25% of all new pension contributions were required to be saved in ways that might help fund new British infrastructure projects, including those linked to the climate crisis, then up to £100bn of funds might be made available for that purpose a year.

A great fear among many people in the UK at present is that Labour might form a new government this year but will not change anything of consequence – because of its commitment to harsh fiscal rules that appear to promise more austerity. This is not necessary. The existing tax system only needs to be made a bit fairer and the funding required to transform our society would be available. Rachel Reeves, please take note.

• Richard Murphy is professor of accounting practice at Sheffield University Management School and director of Tax Research LLP