Cosatu says it wants the next ANC leadership, under Deputy President Cyril Ramaphosa, to be one that is not corruptible.
The federation has endorsed Ramaphosa to take over from President Jacob Zuma when the party holds its 2017 elective conference.
"We want a leader that will unite the movement, (is) comfortable to work with working class leadership, a leader who is not corruptible and doesn't do corruption," the federation's president, Sdumo Dlamini, told the media on Thursday.
Cosatu said it followed these criteria when it gave Ramaphosa the nod to lead the party.
It also looked to his history in the union movement, lauding him for building the National Union of Mineworkers and negotiating the country's constitution.
The federation held a three-day central executive committee meeting and had a "robust and intense" debate on the ANC's succession saga.
It is understood that the debate ended late on Wednesday night.
'There is no free lunch'
Cosatu has no voting powers in the ANC but was instrumental in the election of Zuma at the 2007 and 2012 elective conferences.
It has defended its decision to pronounce on the ANC leadership, despite criticism from the party saying that the federation's members are also members of the ANC and are affected by its decisions.
"The CEC (central executive committee) made it clear that Cosatu is not a junior partner in the alliance and therefore it should not allow any alliance partner to instruct it on what it must do," general secretary Bheki Ntshalintashli said.
However, he said there would be no free ride for Ramaphosa if he wins the ANC presidency.
Ntshalintashli said they wanted him to prioritise worker issues.
"We looked at criteria, but human beings are human beings. We looked to his history, perhaps subjective, but we believe he is in a position to help the ANC... But there is no free lunch; as soon as he goes to power we will talk to him about what to deliver."
'Cyril was not found guilty'
Cosatu dismissed criticism of Ramaphosa after an email communication emerged during the Marikana Commission that he had pushed for government action to end the strike by the Associated Mine Workers Union (AMCU).
Cosatu's second deputy president Zingizwa Losi said the commission of inquiry into the massacre, that left 34 miners dead after police fired at them in 2012, had not found Ramaphosa guilty.
She said the criticism would be pushed by opposition parties who wanted regime change.
"You keep raising Marikana when (the) commission was put in place and Cyril was not found guilty. Things will be raised, it doesn't matter who leads the ANC, (this) war is not against individuals, but (against the) ANC. They want regime change."
Cosatu would not comment on calls by its affiliates that Zuma must step down.
It said it would rather engage with the ANC's national working committee.
It had also not decided on who should be part of the Ramaphosa leadership team.Suggest a correction