LABOUR’S proposed “oligarch levy” to tax the secret offshore purchases of property in Britain could generate more than £3 billion a year from “suspicious wealth” for the Treasury, the party said yesterday.

Shadow chancellor John McDonnell announced it was “time to call an end to the use of our financial system and property market as a hiding place for rich foreign oligarchs” by enforcing unexplained wealth orders and extending transparency of British-owned companies to known tax havens.

Mr McDonnell is also calling for the “politically exposed person” regime to be tightened up and the introduction of a so-called “Magnitsky clause” to apply sanctions against human rights abusers. The clause is named after a whistleblowing accountant who died in jail in 2009.