The state of the tripartite alliance and the national planning commission are among matters expected to be discussed at Cosatu's four-day conference which starts in Midrand on Monday.

The 10th national congress would be opened by Congress of SA Trade Unions president Sidumo Dlamini, with a key note address by President Jacob Zuma.

A political report would be presented by Cosatu general secretary Zwelinzima Vavi. Cosatu alliance partner, the SA Communist Party's general secretary Blade Nzimande was also expected to address the gathering.

Vavi's political report would delve into the "subjective and objective" weaknesses of the ruling tripartite alliance. While relations had improved between alliance partners under the Zuma administration, criticism and tension between them remained on certain issues.

Last week Cosatu expressed fears that Minister in the Presidency Trevor Manuel was accumulating too much power. Manuel, in charge of the national planning commission, recently released a green paper on strategic planning. Cosatu said if the former finance minister's plans were acted on, he would become the country's de facto "imperial" prime minister.

In June the SA Communist Party and Cosatu also lambasted Manuel for suggesting trade unions were exacerbating the global economic crisis with their strikes.

The Mail & Guardian on Friday quoted Cosatu president Sidumo Dlamini as saying Manuel was the last "hope" for the revival of the group described as the "1996 class project", or former president Thabo Mbeki's supporters.

He told the newspaper Manuel was using the planning commission to position himself as "second in charge".

"He wants to be seen again as this super-minister and every minister should go to him, bow his head and say, 'Please, Mr Manuel, can we have this?'" Dlamini was quoted as saying.

The ruling party backed Manuel after the labour federation's criticism, saying "principles rather than individual personalities" should be debated.

The national planning commission would also feature in Vavi's political report. Other issues to be covered in the report included attempts to divide the alliance, macro-economic policy, the proposed National Health Insurance scheme and the recent spate of industrial action. The congress would further tackle unionists with business interests and corruption.

It concludes on Thursday.