Hong Kong stocks suffered their biggest one-day fall in a month on Monday, hurt by a slump in mainland Chinese companies listed in the city and on concerns over the impact of Britain's exit from the European Union.

The benchmark Hang Seng index dropped 1.0 percent, to 22,718.15 points.

The Hong Kong China Enterprises Index, which tracks mainland-based companies, was down a sharper 1.2 percent, to 9,666.09 points.

Hong Kong tracked Asian markets lower, partly due to what dealers said was reaction to media reports that UK Prime Minister Theresa May would use a speech on Tuesday to signal plans for a "hard Brexit", in which border control is prioritised over market access.

The city's bourse is more exposed to global fund flows than mainland markets, and therefore is sensitive to news events affecting broad risk appetite.

Nearly all sectors on the Hong Kong bourse lost ground, but utility stocks tacked on a modest 0.2 percent after receiving a boost from Power Assets Holdings Ltd which added nearly 3 percent.

Telecommunication firms and oil majors that had rallied earlier on restructuring hopes corrected under profit-taking pressure.

Shares of index heavyweights China Unicom Hong Kong Ltd, China Mobile Ltd , PetroChina Co Ltd and CNOOC Ltd all fell.