The researcher's team had made frequent trips to the city to interview residents about their opinions on the influx.

The news comes days after Chief Executive Leung Chun-ying sought input from members of the Commission on Strategic Development over the possibility of a 20 per cent cut in the 40 million mainlanders visiting Hong Kong every year.

Leung later played down suggestions the government was considering cutting the number of mainland visitors, saying it was merely considering views about how to handle the influx, which it projects will reach 100 million annually by 2020.

A Hong Kong government source said the chief executive raised the figure of 20 per cent only to prompt discussion. No decision has been made on what reductions, if any, should be made on the number of mainland tourists.

The mainland researcher said that it was up to the Hong Kong government to propose any such reduction. "The central government would not hesitate to approve whatever proposal is put forward by the Hong Kong government," said the researcher.

Beijing increased intelligence gathering on Hong Kong after half a million people took to the streets on July 1, 2003 to oppose a national security law that critics said would have limited people's freedom. The scale of the protest caught the Hong Kong and central governments off guard and forced the authorities to shelve the plan.

Since then, Beijing has regularly dispatched researchers to talk to people from all walks of life in Hong Kong. They regularly submit reports based on their observations and interviews.

In March, Zhang Dejiang, chairman of the National People's Congress, told a closed meeting with Hong Kong deputies at the annual NPC session in Beijing that Hong Kong's capacity to welcome mainland tourists was a matter of concern for the central government.