The Johnson-backed report, titled London: The Global Powerhouse, says that if the UK forges ties with new markets and maintains its competitive edge, London can overcome competition from rival global cities such as Singapore, Shanghai and New York.
“[London’s] main competitor is often seen as Paris, itself a great city, but not matching London in the 21st century [because of] the drag from high taxes, euro membership and high unemployment,” the report said.
“While Paris may be our closest competitor in Europe, New York is the biggest challenger to London in the western hemisphere," it added.
Gerard Lyons, one of the mayor's economic advisers, noted that the UK can only keep its position in the world if it continues to invest in infrastructure, including new transport links and the issue of housing supply.
"The biggest issue is that London is an expensive place to live and from which to do business. London needs housing. It needs to expand eastwards, possibly upwards and outwards," he said.
“Whether the UK is in or out of the EU is not the only issue for future success, but it depends heavily on the policies pursued whether we are in or out," the report said.
If the UK does remain in the EU, there will still be issues to resolve, the report adds.
"Not joining the euro had been one of the biggest policy success stories of recent times. It is vital for London that if the UK remains in the EU that the future relationship between the eurozone and the non-eurozone economies is safeguarded, in order to protect the City," it noted.
The report comes after economists at UBS said the British pound could fall to parity with the euro if the UK does decide to leave the. The same economists reckon there's a 40 per cent change that the UK will vote for Brexit.
Johnson has already come out as backing Brexit, insisting it is the best move for London and the country as a whole. However, cynics have said that his decision was based on political motivations for Number 10.