In a follow-up letter to the secretary of state for business, energy and industrial strategy Greg Clark –having previously contacted him back in May last year – Mr Khan expressed his frustration over the government’s slow progress.

 The mayor of London pointed out that ministers had first committed to a public register of the beneficial owners of UK registered companies in 2013.

It then took another three years for the commitment to expand to include foreign companies that own property in the UK.

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In January it was announced that the register will not be operational until 2021.

 “The government’s slow pace of progress on this issue has been bitterly disappointing,” said Mr Khan.

“If the proposed timetable slips even slightly, the publication of this much-needed register could easily have taken a decade since a commitment to greater transparency was first made by the prime minister at the time.

“For an issue which is of such importance in London, this is completely unacceptable.”

Mr Khan urged the government to prioritise the publication of draft legislation and asked the prime minister to give it full backing in parliament.