HONG KONG — Hong Kong stockbrokers protested on Tuesday in a last-ditch attempt to stop the city’s stock market operator from trimming their lunch break from 90 minutes to an hour.

Waving cutout figures of the stock exchange’s CEO and its chairman, about 150 protesters walked through the central business district to the stock exchange and on to government headquarters.

Hong Kong Exchanges and Clearing Ltd., which operates the southern Chinese financial center’s stock market, plans to reduce the break to one hour starting Monday. It’s the second stage of a plan that began last year by trimming an hour from the 2 1/2 hour trading break.

The change is aimed at stepping up competitiveness by bringing trading hours in line with rival bourses in Asia and the West. But protesters, most of whom were from Hong Kong’s many small brokerages, complained they won’t have enough time to talk with clients, research stocks or attend presentations on initial public offerings.

The brokers tried to dispel the popular notion that they spend their time smoking cigars and drinking fine wines during long leisurely lunches at swanky restaurants.

“I actually bring along my lunch box,” said Danny Lam, an account executive at Kingston Securities. “Our lunch hour can be very stressful as well. We still have to rush.”

Playing the stock market is a popular pastime in freewheeling, avowedly capitalist Hong Kong. Many of the city’s 500 registered brokers are small companies that serve individual investors, often operating from storefront offices where clients, usually elderly, like to spend time trading.

Staff at small brokerages say that they don’t have the resources of big global banks, which operate from gleaming skyscrapers and mainly serve institutional investors with big teams of back office staff. They fear the exchange’s reforms could spell the end for small dealers.

“Maybe the securities firms will get less income, so maybe the result is that some bosses of securities firms cannot see any future in this field,” said Patrick Lam, chairman of the Hong Kong Securities and Futures Employees Union. “Maybe they’ll close down the business.”

Last year, Tokyo’s stock exchange shortened its lunch break while Singapore eliminated its altogether. Major stock markets in the United States, Britain, France and Germany don’t stop for lunch.

The Hong Kong exchange has tried to introduce longer trading hours before. An attempt in 2003 failed because of stiff opposition from brokers but this time the shorter lunch break looks certain to begin as scheduled on Monday.