Lobby group Afriforum has found that the City of Tshwane's R37 billion budget, which was approved by the metro's administrator Mpho Nawa on 30 June, violated the Constitution.
This comes in light of Tshwane residents' frustrations over the metro's new fixed charges for water and sanitation bills.
The residents have raised their concern about the excessively high municipal bills with former local ward councillor Yolanda Duvenhage, who confirmed that she had received more than 500 complaints.
Afriforum had challenged the matter, suggesting that Nawa exceeded his powers by approving the metro's budget.
Afriforum's local government affairs manager Morné Mostert said on Wednesday during a press briefing: "In carrying out his mandate, the administrator acted outside the law with the approval of the budget, as only a municipal council may approve a final budget."
According to law, in the absence of a legally-constituted city council, only the provincial executive may approve a municipal budget.
Only be a temporary budget can be instilled until the council was reconstituted to approve a final budget.
The metro had been placed under administration in March after cooperative governance MEC Lebogang Maile dissolved the Democratic Alliance (DA) led Tshwane council.
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Afriforum found that Gauteng Premier David Makhura had failed to approve the interim budget.
"The premier should have stepped in immediately to rectify the situation; however, his political ties prevented him from doing so," said Mostert.
Mostert said the organisation have brought a court application forward which request the Gauteng government to set aside the decision to approve the budget.
He added that the application meant that an interim budget must be prepared immediately, while a completely new process must start to approve the new budget.
AfriForum's court application is expected to be heard on 29 September.
"There's has been so much chaos in Tshwane's matter and one example of this mismanagement is the manner in which the metro had changed the tariff structures. The new structure does not only place a greater financial burden on the poor, but discourage consumers from saving water.
"Makhura failed in his duty as chairperson of the provincial executive council (PEC). This resulted in the collapse of the metro's management.
READ MORE: Tshwane budget to be legally challenged as fixed fees infuriate residents
"Although there is litigation on the legality of the decision, he is still under obligation to ensure that the administrator acts within the framework of the Constitution.
"Service delivery deteriorated on various levels, especially in the case of erroneous accounts that were sent out after implementation of the new budget, " he said.
Meanwhile, Afriforum's community affairs strategic advisor, Eugene Brink, urged Tswane residents to protect themselves if the metro sent out erroneous accounts.
"How is it possible that the province focuses on the Tshwane metro while the Merafong or Emfuleni municipalities are in worse condition?
"It is clear that this decision smacks of political opportunism rather than supporting a struggling municipality," he said.
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