Business leaders failing to stand up to unions were "cowards", former Finance Minister Trevor Manuel said at the World Economic Forum meeting in Cape Town.

The website fin24 reported on Friday that Manuel, who is now the head of the National Planning Commission in the Presidency, criticised both business and union leaders.

This was in an address to company bosses, including Sasol chief executive Pat Davies and Old Mutual MD Paul Hanratty.

Manuel seemed to indicate that labour unions were too powerful, the website reported.

"There is no counterweight in society if you have cowards in business," Manuel said. "You have to have counterweights, or you don't make progress."

"You don't have to keel over every time someone stands up and says 'I disagree'," he added.

Davies, however, argued that sometimes the public does not know what goes on behind the scenes.

Most of the times when business leaders give in to union demands, it was upon request from the government, said Davies.

"I have had Cabinet Ministers phoning me to pressure me into solving these issues," said Davies, adding that "you have to pick your battle ground".

Manuel also said unions were using Section 77 of the Labour Relations Act too easily, referring to the Western Cape branch of the Congress of South African Trade Unions (Cosatu) using this to take on Premier Helen Zille's all-male Cabinet.

The provincial Cosatu branch has taken the issue to the National Economic Development and Labour Council under the Section 77 provision.

"If you use this weapon too often you blunt it. The socioeconomic strike is a blunt axe. It's useless," said Manuel.