Suspended Cosatu general secretary Zwelinzima Vavi will challenge his suspension from the trade union federation in the High Court in Johannesburg on Thursday.
In a statement released on Wednesday, Vavi said approaching the court for relief was the last resort.
"As I've said before, we are approaching the courts as a last resort and with a heavy heart," he said in a statement.
"We are however doing so because we believe in the rule of law and that none of us, including the general secretary of Cosatu, is above the law and when he believes his rights are being violated, he, like any worker, is free to approach our courts as the last arbiters."
Vavi was suspended last year after he admitted to having an affair with a junior employee. She initially accused him of rape but did not lay charges with police.
Nine Cosatu affiliates have rallied behind Vavi demanding that he be re-instated.
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