Cosatu is working against the interests of the unemployed and stalling the effort to bring jobs, DA leader Helen Zille said on Tuesday.
In a speech prepared for delivery at a Democratic Alliance Workers Day event in Midvaal, Gauteng, she said the trade union federation was stuck in a 1950s British model of "hostile central bargaining".
It was the only organisation in South Africa that was refusing to take part in programmes to end unemployment.
"Cosatu, which played such a pivotal role in creating South Africa's democracy, runs the risk of being left behind if it remains stuck in the 1950s British model of hostile central bargaining between 'bosses and workers'," Zille said.
"Tragically, Cosatu (alone among the trade union federations) is working against the interests of the unemployed, keeping them permanently locked out, and stalling the effort to bring jobs, redress and reconciliation to our society."
Last week the DA launched an Economic Development Partnership in the Western Cape between business, labour, educational institutions, social movements, NGOs and "countless others" to address problems that impede economic growth and job creation and to remove red tape.
The Congress of SA Trade Unions was the only organisation that would not take part in the process.
"The lesson of our history has been that when we stand together, we can achieve anything. Now we must stand together to defeat unemployment.
"It is sad that Cosatu is the only organisation that will not engage this process, and their members will lose out as a result."
South Africa's official unemployment rate was around 25,7 percent, but the Centre for Development and Enterprise had noted that only 41 percent of the population of working age -- people aged 16 to 64 -- have any kind of job.
What this meant was that there are many more people who were locked out of the job market, than those who had access.
"We agree that trade unions have an important role in a democracy to represent the interests of organised workers. But they are wrong to see managers as their 'class enemy'," she said.
"Countries with growing economies and growing employment have outgrown this 'zero-sum' model where one side's gain is the other side's loss.
"In fact, to create more jobs we need more people who will invest capital and skills, who will take investment risks to open factories and to start businesses, thus creating more jobs," she said.