In a keynote speech at the Institute of Directors, the mayor warned business leaders that ministers appeared to not be listening to their concerns.

“London’s businesses must retain access to the skilled workforce they need in order to grow – it’s absolutely essential to protecting jobs, growth and tax revenues across Britain over the next decade.

“I will keep pushing the government to recognise this vital need in their negotiating position – but it doesn’t look like they are listening.

“If the government ignores the needs of business and pushes ahead with a new system that cuts off access to skilled workers, then we will have no choice but to look at a London-specific solution.”

It was reported that 616,000 of London’s workers were born outside the UK, 12.5% of the workforce.

Around 88,000 of these foreign workers are in construction, 49,000 in financial and insurance activities and 58,000 in professional, scientific and technical activities.

Mr Khan added: “We need to redouble our efforts to train up today’s young Londoners for the jobs of tomorrow.

“That is why I have pushed for devolution of skills provision in London so we can better align skills training with the roles that our companies need.

“The City of London Corporation and London Chambers of Commerce have already done some crucial early thinking about options – but we need to go further and faster to make the case to the government and develop a new system.

“I will bring together industry leaders, business representatives and experts at City Hall in the new year to take this vital work forward.”