“This is the first time that Solidarity subpoenaed a minister to explain his decision in court," deputy general secretary Johan Kruger said in a statement.

Government spokeswoman Phumla Williams said she was not immediately aware of the subpoena, but would comment on the matter later.

The union is representing magistrate Martin Kroukamp, claiming he was overlooked for a position at Alberton Magistrate's Court on the basis of his race.

Kruger said that according to the information received by Solidarity, the Magistrate's Commission had allegedly recommended Kroukamp as the only suitable candidate.

Solidarity contends that Radebe ignored the Commission's recommendation, saying that Kroukamp's promotion would not promote transformation.

"In our summons to the minister, we requested that he should provide evidence to support his decision not to promote magistrate Kroukamp,” Kruger said.

“For Solidarity, the crux of the matter is not merely magistrate Kroukamp's rights, but each and every South African's right to an effective judicial system."