By Sumeet Chatterjee and Scott Murdoch

HONG KONG (Reuters) - China's plan to impose national security legislation in Hong Kong is expected to lead to the flight of capital and talent from the Asian financial hub, bankers and headhunters said on Friday.

The proposed legislation, which prompted concerns over freedoms in the semi-autonomous city, comes after large-scale and often violent pro-democracy demonstrations last year, which had already pushed some wealthy individuals to scout for investment options elsewhere.

"In some cases where clients had a bit of inertia and hoped things that happened last year will just go away, they will now step on the gas to reduce their wealth concentration risk here," said a senior banker at a European private bank.

"In many cases last year, we saw our clients putting in place plan B and didn't quite move the assets out of Hong Kong. I have already received some enquiries to activate that plan now," said the banker, whose firm manages more than $200 billion in assets.

The banker declined to be identified as he is not authorised to speak to the media.

Hong Kong's main stock market index fell over 5% on Friday.

Globally, Hong Kong ranked second in wealth per adult after Switzerland in mid-2019, and the city ranked 10th in terms of the number of ultra-high net worth individuals or those with more than $50 million in assets, according to a Credit Suisse report.

Hong Kong competes fiercely with Singapore to be considered Asia's premier financial centre. Global private banks including Credit Suisse and UBS, as well as Asian wealth managers have their regional operations in the two hubs.

"We have had instances where clients were considering establishing a presence in Hong Kong ... but due to the pro-democracy protests in 2019, they decided to set up a presence in Singapore instead," said Rahul Sen, London-based partner for wealth management headhunting and consulting firm Boyden.

"Existing banks in Hong Kong will also look at increasing their Greater China coverage from Singapore if the protests last longer or a feasible solution is not sought."

The American Chamber of Commerce (AmCham) in Hong Kong said the enactment of the law could "jeopardize future prospects" for international business, particularly if details are not spelled out.

"No one wins if the foundation for Hong Kong's role as a prime international business and financial centre is eroded," Robert Grieves, chairman of AmCham in Hong Kong said in a statement.