New York has extended its lead as the world's top financial centre, with London barely holding on to second place ahead of Hong Kong as uncertainty over Brexit takes its toll on the UK capital, a Z/Yen Group survey for 2019 showed on Thursday.

New York extended its lead over London to 17 points, while a strong performance from other centres, in particular, Paris, put London’s second place in the index at risk, compilers of the Global Financial Centres Index (GFCI) said in a statement.

Hong Kong is now just two points behind London where a key issue for finance professional is whether Britain's departure from the European Union on Oct. 31 will impede the free movement of talent, it added.

The GFCI index rated 114 financial centres, combining assessments from finance sector professionals with data.

"Respondents consider that New York, Hong Kong, and Singapore will benefit substantially from Brexit. In Europe, Frankfurt is considered likely to benefit most, followed by Paris, Luxembourg, Zurich, and Dublin."

Singapore, Shanghai, Tokyo, Beijing, Dubai, Shenzhen, and Sydney make up the remainder of the top 10 centres. The rise of Shenzhen, Dubai and Sydney eased out Toronto, Zurich and Frankfurt from the top 10.

"Competition at the top of the GFCI is intense. London remains second, but the signs for the future are worrying with Asian and other European centres showing strongly," said Michael Mainelli, executive chairman of Z/Yen.

"Policy uncertainty, Brexit, trade wars and geopolitical unrest are causing more volatility in financial centre performance."

It also published an index ranking financial centres as competitive places for fin-tech companies for the first time, with Beijing and Shanghai leading, with New York, London, Singapore, San Francisco and Chicago in the top 10.

The survey is being launched on Thursday in London by Z/Yen Group in partnership with the China Development Institute.