"Once more, (the statistics) reaffirm the finding that South Africa has the highest unemployment rate of any middle-income country," Cosatu said in a statement.
Statistics SA announced on Wednesday that the official unemployment rate for February this year was 29.4%, marginally down from 29.5% in September last year.
In the expanded definition of unemployment - including discouraged jobseekers - the rate stood at 40.9%.
The expanded definition includes those economically active South Africans between the ages of 15 and 65 who are willing and able to work, but who had not tried to find employment four weeks prior to being surveyed.
The persistence of high levels of unemployment was one reason why Cosatu called on people to join its general strike next Tuesday and Wednesday against privatisation, poverty and joblessness, the statement said.
"Cosatu rejects the argument that mass unemployment is caused by inadequate skills. That contention ignores the fact that young people have the highest rate of unemployment - and also a higher educational level, by far, than the average employed person.
"The main cause of high unemployment remains the structure of the economy, which favours large, capital-intensive enterprises and makes South Africa one of the most unequal countries in the world."
This situation was exacerbated by the refusal of big business to increase its investment in South Africa, Cosatu said.