Labour has announced it will impose a "Robin Hood Tax" on financial transactions if it gains power in the general election on 8 June.
The levy would extend a current 0.5% stamp duty on the exchange of shares to other forms of trading such as options and derivatives.
Shadow chancellor John McDonnell said the measure will bring in over £26bn ($33.5bn) over the next parliament, and will fund Labour's expansive spending proposals.
Last week, a leaked copy of the party's manifesto revealed that Labour planned to spend an additional £6bn on the NHS and £1.6bn on social care in addition to scrapping university tuition fees and building 100,000 new council houses a year. It also plans to re-nationalise energy, rail and mail services.
Announcing the levy, McDonnell said the policy would "make the financial sector pay its fair share after it received huge public bailouts in the crash".
He added: "All we're asking for is fairness in our tax system. By making those who trade in financial derivatives pay a small fraction of their profits, we can help properly fund our public services.
"Ordinary people are still being made to pay by the Tories for a crisis they didn't cause through the worst spending cuts for generations."
Labour also said it would launch "the biggest crackdown in this country's history" on tax avoidance by closing loopholes as well as clamping down on shell companies and offshore jurisdictions with low-tax regimes.
The proposals will likely see resistance from the City of London and the financial sector – already faced with uncertainty due to Brexit – as they will see their profits take a hit.
Labour also said it would require people earning over £1m to file their tax returns publicly and for "large companies" to file their tax return publicly on Companies House.
In a statement, the Conservatives branded the proposals a "shambles".