Jeremy Corbyn

If this plan becomes law 21,000 Brits will be affected, according to calculations by the Institute for Fiscal Studies (IFS).

Such a change would also mark a pivotal change in British tax policy, eradicating the notion that everyone’s tax affairs are private.

The plan is detailed in Labour’s Fair Tax Programme located on the party’s website.

The document states: “The public has lost faith that our tax system is a level playing field, with multinationals dodging tax and the wealthy getting away with contributing very little. Labour will erode this secrecy by making the tax returns of wealthy individuals publicly available.

“This system of public filing, following the lead of Scandinavian countries, should inform public debate on income and wealth inequality.”

However, accountants say there is a difference between the Scandinavian model and what Labour is proposing. In Scandinavia, everyone has their details published, not just the wealthy, The Times reports.

Mike Hodges, a partner at Saffery Champness, said a possible legal challenge to Labour’s proposal could be one of “justifying revealing one demographic’s personal information but not another’s”.

He said: “For generations the UK system has worked on complete confidentiality, with HM Revenue & Customs ensuring that no one’s tax affairs are ever discussed externally.”