McDonald's and KFC have promised to set up trade unions this year for their outlets in Guangdong, the country's top trade union said on Thursday.

Hang Yuan, a spokeswoman with the All-China Federation of Trade Unions (ACFTU), said the fast-food companies made the promise earlier this year after negotiating with the Guangdong provincial trade union.

Kong Xianghong, a senior official with the Guangdong provincial trade union, was quoted by Xinhua News Agency as saying that McDonald's had promised to set up trade union branches at its outlets in the province by June.

However, a spokesman for McDonald's in Guangdong said on Thursday he would not confirm that the company was establishing union branches.

Kong said that a preparations group, including representatives of employees and the management, had already been established.

McDonald's, however, refused to deny or confirm the group's existence.

The fast-food giants have recently been criticized for underpaying their part-time workers.

"We will continue to help foreign-funded enterprises set up trade unions, which is the best way to protect workers' rights and interests, and improve labor-management relations," Hang said.

About 26 percent of China's 150,000 overseas-invested companies have set up trade unions, which have a total membership of 4.29 million.

According to the Law of Trade Unions, which was promulgated in 1992, trade unions are formed by employees voluntarily. No organization or individual can obstruct or restrict them from joining a union.

"We can draw a lesson from these recent cases that in enterprises without trade unions, workers' rights and interests can't be protected," Hang said.

The federation said on Tuesday that fast-food giants including McDonald's, KFC and Pizza Hut had violated labor laws by paying part-time workers in Guangzhou much less than the local minimum wage of about 1 U.S. dollars an hour.

A statement from McDonald's (China) late on Wednesday said the company had always strictly abided by all national and local laws and regulations.

It went on to say that the company was "deeply surprised" that the ACFTU had alleged it had violated labor laws. It said the ACFTU had been "imprudent" in making such allegations.