Thousands of Brexit backers want Sadiq Khan to be removed as London mayor
Mr Khan has urged the Government to give the capital "a voice at the table" during upcoming negotiations with Brussels.
And he wants to introduce special work visa for migrants coming to work in London.
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But his position has angered Brexit supporters.
More than 47,000 have signed Matthew Lee's petition on Change.org calling for the Mayor to be removed.
He claims Mr Khan's comments are encouraging the growing movement for London to become independent from the UK.
Sadiq Khan elected London Mayor Sat, May 7, 2016
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Sadiq Khan sworn into office
Mr Lee said: "As the Mayor of London, Sadiq Khan has a position of power in the capital.
"He should be discouraging any such action from those who wish to create London as an independent state.
"London is the capital city of the United Kingdom and not the European Union."
Securing access to the single market is critical for London
In a doom-mongering speech last month, Mr Khan claimed a hard Brexit "could tear Britain apart".
He said: "Securing privileged access to the single market must be the top priority for the negotiations.
"It's critical for London. Nothing else will do. It can't be brushed aside."
The Mayor added: "A hard Brexit would cut Europe off from its only truly global financial center.
"This would be bad news for Europe as well as Britain. So a hard Brexit really would be a lose-lose situation.
"But I'm confident that despite the Prime Minister's rhetoric, there is still a sensible deal to be done."
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