A prominent lawyer says parliament's vote to approve President Salva Kiir's 28 states order is unconstitutional.

Agok Makur, a lawyer for an alliance of South Sudan opposition parties who went to constitutional court to halt the 28 states order, said the vote to amend the constitution in favor of the order violates Article 54 of the constitution, which relate to parliament's conduct of business regulations.

Citing the parliament's conduct of business regulations, he said says that if challenged constitutional amendments must be suspended until a court issues a final ruling.

Agok said parliament had been notified of the lawsuit brought against Kiir's Order, and that the constitutional court is set to hear the political parties' petition on 1 December.