The Congress of South African Trade Unions' (Cosatu's) statement that Minister in the Presidency Trevor Manuel could become a de facto "imperial" prime minister, was unfortunate, the African National Congress (ANC) said on Thursday.

"Attacks on the personality of... Manuel by Cosatu... [are] unfortunate and worrisome," said party spokesperson Ishmael Mnisi in a statement.

Wednesday's edition of Business Day detailed a Cosatu report which warned that Manuel, who is responsible for national planning, was accumulating too much power.

It said if his intentions for the National Planning Commission were carried out, he would become the country's de facto "imperial" prime minister.

The report was an analysis of a green paper on national strategic planning which Manuel released earlier this month.

"Debate principles rather than individual personalities," said Mnisi.

"This will ensure that we have a better and a healthy discourse which will lead to better solutions for our country."

Mnisi said the green paper on the establishment of the national planning commission and the policy document on performance monitoring and evaluation were released as discussion documents to "kick-start" discussion on improving government's effectiveness.

"Once consultations on these issues are completed, the process to set up the high level structures will commence," he said.