The ANC leadership in Gauteng meets on Wednesday to nominate a successor to outgoing premier Mbhazima Shilowa, who has been branded a hypocrite by his former trade union movement.

Shilowa announced his resignation on Monday, saying it was out of loyalty to ousted president Thabo Mbeki, who was removed from office by the national executive committee of the African National Congress.

The Congress of SA Trade Unions, of which Shilowa is a former general secretary, lashed out at him on Wednesday, describing his criticism of the ANC as “unbecoming behaviour”.

Cosatu welcomed his resignation and said he must leave office immediately. “We believe that we can’t entrust ill-disciplined cadres with the responsibility of being the guardians of the state resources.”

It was “unacceptable” that Shilowa said he would find it difficult to defend the decision of the national executive committee of the ANC to remove Mbeki from office.

“We are not taking kindly his continuous criticism of that decision to recall Thabo Mbeki… He does not have any authority to lambaste the ANC NEC decision in public,” Cosatu said.

The trade union movement traced past comments by Shilowa as far back as 1999, when he, according to the statement, said he would “make mincemeat of Cosatu if it ever makes his life difficult as premier”.

In announcing his resignation, Shilowa said: “I am resigning due to my convictions that while the ANC has the right to recall any of its deployed cadres, the decision needs to be based on solid facts, be fair and just.

“I also did not feel that I will be able to, with conviction, publicly explain or defend the NEC’s decision on comrade Thabo Mbeki. “You stand by your own if you think they’ve been wrongly dealt with. I’m doing no more than that,” he added.

The ANC, in a statement on Tuesday, said: “As the ANC we disapprove of this unbecoming behaviour of a long-serving ANC member. “We expect comrade Shilowa to observe discipline, behave honestly and carry out loyally the decisions of the majority and of higher bodies.”

The ANC provincial executive committee will nominate three candidates at a meeting, starting at 3pm, to take over from Shilowa, said spokesman Nkenke Kekana. The names would be forwarded to the national leadership for a decision.

Media reports have suggested the front-runners to be finance MEC Paul Mashatile, chairman of the province, and education MEC Angie Motshekga.

The name of the new Gauteng premier would be known “at the earliest, by Friday”, said Kekana. Meanwhile, the opposition Democratic Alliance defended Shilowa’s legacy in a statement on Wednesday, and described the attacks on him as extraordinary.

“How is it that despite Shilowa’s earlier immense popularity in the ANC in Gauteng, there is not a single ANC member who is now willing to defend him?,” asked DA Gauteng leader Jack Bloom.

“The ANC’s Stalinist slip is showing. This not a party where Shilowa belongs,” said Bloom.