A coalition of over 50 business associations is planning to take out advertisements to spell out their objections to the introduction of standard working hours.
The plan came under fire from labour activists who say the coalition is trying to exert pressure on the government.
The move comes amid expectations of the launch by the government this month of a task force to examine the impact of a law regulating work hours. A source said the task force would consist of about 24 people, and all 12 members of the Labour Advisory Board had been invited to join.
The Hong Kong Business Community Joint Conference has written to its members asking for support and donations to pay for the ads in three Chinese-language newspapers on April 17.
In the letter, it warns that a limit on working hours before overtime has to be paid would have "a huge impact on society and business".
It says it goes against the city's free-market principles which offer maximum room for companies to develop.
"Setting standard working hours is a complex, controversial issue, which needs in-depth discussion from all sides of society," the letter says. It questions how hours can be standardised across the vast range of occupations.
"If working hours are standardised through legislation, business costs will increase significantly and the competitiveness of small to medium-sized companies will be weakened," it said. "The minimum-wage law was introduced not long ago, and both the business and labour sectors, as well as other sectors in society, still need time to absorb the impact of that law."
The coalition's members mostly represent medium-sized businesses. They include the Hong Kong Jewellery Manufacturers' Association and the Hong Kong Small and Medium Enterprises General Association.
Seven of the city's biggest business chambers, including the Hong Kong General Chamber of Commerce, issued a joint letter to the government in November last year warning laws regulating working hours would hurt business.
Confederation of Trade Unions policy researcher Poon Man-hon argued these fears were unfounded.
The veteran analyst said his studies showed that the rise in labour costs would be only 4.5 per cent - as long as the law did not apply to management, who earned more than the general workforce.
"Studies in other countries show the positive impact of such a law," he said. "The workers have a better sense of belonging and the turnover rate is lower. There is also less sick leave."
He added: "The coalition is exerting pressure on the government. It's not rational. I think they feel they need to take a stronger stand on this matter after the minimum wage law went through."
Labour Advisory Board employee representative Lee Tak-ming suggested setting standard working hours at 46 to 48 hours weekly and that overtime pay for workers in different industries should be different.
For example, people in more physically demanding, low-paid jobs, such as cleaners, should be paid 1.5 times the hourly wage for overtime work, he said.
The government estimated in a report released last November that employers would need to pay out up to HK$55.2 billion more a year in wages if working hours were regulated.