Trade unionist lawmaker Lam Chun-sing on Tuesday questioned why the government needs to use a new labour importation scheme to bring in thousands of construction and transport workers.

He was speaking to RTHK after officials announced plans to bring in as many as 12,000 construction workers - with priority given to those working in the public sector - with the transport industry given a quota of 8,000 to fill vacancies for airport staff and drivers.

However, the chair of the Federation of Hong Kong and Kowloon Labour Unions said he's worried that this is just the start, and that more schemes will be established for other industries in future that bypass current vetting.

He said under the current Supplementary Labour Scheme, representatives of employers and employees discuss the cases where there's an application to import labour.

"Maybe later ... different industries will have their own importation of labour schemes so there is no need for the Labour Advisory Board and the Labour Department to monitor [them] to ensure the priority of local labour employment," he said.

In announcing the plan, Deputy Financial Secretary Michael Wong dismissed suggestions that the outside staff would put locals at a disadvantage, saying the non-local workers’ pay must not be lower than the median wage of their local counterparts.

But Lam said in the importation of care home workers last year, some companies and employment agencies had demanded that carers brought into Hong Kong pay them some of the market-rate salary they received.

"So in the long-term, they will encourage the employer to use cheap labour," he said.

"They do not have any incentive to improve the benefit and salary of local labour."

Lam urged the government to establish a timetable to suspend and review the new schemes.