London retains crown as the world's top 'city of opportunity' for now - but Brexit could be its undoing

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London has retained its crown as the world's top city of opportunity for the second year in a row, but faces major 'challenges' in Brexit's aftermath, research suggests.

In terms of economic importance, reputation as a city gateway, the ease of doing business, innovation and culture, London comes out on top in PricewaterhouseCooper's latest Cities of Opportunity Index.

The report - which was compiled before the EU referendum - also found it significantly extended its lead in the index, with a 6.5 per cent advantage over its closest rival Singapore. It also kept the top spot for economic clout, beating fellow global powerhouses New York and Beijing. 

A world of opportunity: London has retained its crown as the world's top city of opportunity for the second year in a row, but faces major 'challenges' in Brexit's aftermath, PwC says

But experts at PwC have warned the capital's reputation risks being damaged by Brexit - possibly hitting recruitment, trade and regulation. 

Sadiq Khan, the Mayor of London, said: 'This is the best city in the world; it's open for business, creative, entrepreneurial, agile, full of opportunity and a hub for business and leisure travel.

'Despite the recent vote to leave the European Union, there is no doubt that this will continue to be the best place in the world to do business.' 

The index also found London performed strongly for the quality of universities and access to libraries and is one of the top cities best suited for young people aged between 15 and 29.

It also came top in its attractiveness to employees looking to relocate, according to PwC.

While London came out on top in the opportunity stakes, it was also found to be the world's most expensive city in terms of the cost of living and business occupancy.

Warnings: Experts at PwC warned there were risks Brexit could hit London hard

The three most affordable cities in the world include Johannesburg, Toronto and Los Angeles, PwC said.

David Snell, a partner at PwC, said: 'Change is ahead and it remains to be seen what impact the UK's decision to leave the EU will have on our vibrant city.'

He added that the Brexit negotiations would offer a 'major opportunity for financial services firms to work with regulators, investors and clients in order to shape a new rulebook fit for the new climate.'