Speaking among business leaders to demand more autonomy for London, Khan said that further devolution would be to the benefit of the whole country.
"As much as I might like the idea of a London city state, I'm not seriously talking about independence today. I am not planning to install border points on the M25," Khan said.
"But on behalf of all Londoners, I am demanding more autonomy for the capital - right now. More autonomy in order to protect London's economy from the uncertainty ahead, to protect the businesses from around the world who trade here and to protect our jobs, wealth and prosperity."
Khan is seeking devolution over fiscal responsibility including tax raising power, as well as more control over business and skills, housing and planning, transport, health and policing and criminal justice.
He said that he wasn’t “asking for London to get a bigger slice of the British pie”, only for Londoners to “get more control over the slice of the pie we already get.”
Leader of the Liberal Democrats at the London Assembly said: “I stand shoulder to shoulder with the Mayor in his call for more devolution of powers to London and most importantly greater say over how taxes raised in the capital are spent.
“London lags behind many international cities in the proportion of taxes paid by individuals and businesses that is directly retained by the Mayor and the boroughs.
“There was a powerful case for more powers being devolved to London before the European referendum. The case for London now having greater control over its future is overwhelming.”
Khan also garnered the support of the Conservatives. Tory group leader Gareth Bacon AM said: “There are clear benefits to London taking additional control of powers in some areas such as those set out by the London Finance Commission when Boris Johnson was mayor.
“I welcome Sadiq Khan’s support for the measures that Boris Johnson proposed. This is something that has been on the table for a long time however and the Mayor didn’t give any real detail as to how he will work with central government to deliver this devolution.
“If he’s serious about making things happen for London he will need to come up with a definitive plan and I look forward to hearing the details.”
"Remaining in the single market needs to be priority one, two and three of our negotiation with the EU," Khan continued, adding: "And London - as the beating heart of the UK’s financial sector - and the only region of England which voted to Remain - simply has to have a seat at the negotiations."
Baroness Jo Valentine, chief executive of London First, said: “The mayor is right that we must remain part of the single market. London businesses are absolutely clear this is critical to protecting jobs and prosperity, not just in the capital but across the whole of the UK.
"We also need London to keep the economic engine running by having the levers to drive forward projects such as Crossrail 2, doubling housebuilding and improving skill levels. Where the mayor needs more powers to act, he should be given them.”
Earlier this week Khan said that he would fight passporting rights. He told City A.M. the loss of passporting – the system that allows UK-regulated banks to operate across the EU – would be “a disaster”.