Tourism Board chairman James Tien Pei-chun says a change of rules which would give 4.1 million non-permanent citizens of Shenzhen easier access to Hong Kong should be postponed.
He warned many of the new visitors could take jobs illegally or become cross-border traders.
His appeal surprised fellow members of the tourism body, one of whom linked the remarks to Tien's electoral ambitions.
He is running to regain the New Territories East seat he lost in 2008 in next month's Legislative Council election.
Tien said in a radio interview that many of the 2.8 million Shenzhen permanent residents who are already allowed to apply for multi-entry permits for Hong Kong worked as parallel traders, buying goods in the city and selling them on the mainland.
"They are not tourists. They are illegal workers," he said. Tien said the announcement last week that multiple-entry permits would be opened up to those who do not hold hukou, or residency certificates, in the border boomtown - many of them poor migrant workers - would lead to an influx of visitors who are not "conventional tourists".
The new visitors would have less purchasing power and would be stocking up on goods like baby formula instead of visiting the city's theme parks, he said.
Michael Wu Siu-ieng, a board member of the Tourism Board and chairman of the Travel Industry Council, said: "As a global tourism hub, Hong Kong should welcome visitors from anywhere."
Fellow board member Ko Chi-sum asked of Tien: "Did he say that because of the election?"
Wong Sing-chi, a Democratic Party incumbent and election rival of Tien's, also called for the rule change to be shelved. But the New Territories Association of Societies said the rules should be relaxed gradually and the impact on Hong Kong considered.
Gary Chan Hak-kan, another lawmaker seeking re-election, is an executive of the association and a member of the Democratic Alliance for the Betterment and Progress of Hong Kong.
The Federation of Trade Unions, whose candidate in New Territories East is Ip Wai-ming, called for better communication between Hong Kong and Shenzhen leaders.
Secretary for Labour and Welfare Matthew Cheung Kin-chung said the relaxation would benefit the retail and catering industries. The government would step up prosecution of illegal workers.
Executive councillor Bernard Chan said the government should inform its mainland counterpart of the city's maximum capacity for handling mainland tourists and improve cross-border communications on social issues.
"Communications across the border have been focused on economic issues. But with more integration and more conflicts, the government has to be more mindful of handling the cross-border issues, which also cover medical services and education," he said.
Other candidates for New Territories East are "Long Hair" Leung Kwok-hung, Emily Lau Wai-hing, Angel Leung On-kay, Scarlett Pong Oi-lan, Elizabeth Quat, Raymond Chan Chi-chuen, Yau Wing-kwong, Dr Fernando Cheung Chiu-hung, Richard Tsoi Yiu-cheong, Gary Fan Kwok-wai, Raymond Ho Man-kit, Ronny Tong Ka-wah, Pong Yat-ming, Christine Fong Kwok-shan and Chan Kwok-keung.