Jakarta. Presidential candidate Prabowo Subianto's relentless claims of electoral fraud and political bias have the Constitutional Court uneasy, raising concern that the former Army general is working actively to undermine Indonesia's established system of democracy. 

The Constitutional Court issued a statement on Thursday dismissing any notion that doubts the court's impartiality, following a remark by the Prabowo camp dismissing the court as "useless" for resolving election disputes. 

Indonesia's 1945 Constitution states that the Constitutional Court is the only institution with the authority to decide disputes involving election results.

"The judiciary in the Constitutional Court is open to the public. The process is transparent. The public can always monitor it," court spokesman Fajar Laksono said in a statement. 

He added that it was up to the candidates to bring their election disputes to the court.

"So what is needed, is convincing argumentation, witnesses, evidence; not mere claims or assumptions," he said.

Prabowo, who is trailing the incumbent, President Joko "Jokowi" Widodo, by 12 percentage points in the official tally, said on Tuesday that he would not concede to any result announced by the General Elections Commission (KPU), repeating claims of massive fraud in the election.

His right-hand man, Fadli Zon, who is also deputy chairman of Prabowo's Great Indonesia Movement Party (Gerindra), said the presidential candidate is unlikely to bring election disputes to the Constitutional Court.

"In 2014, we followed that path and we saw that the Constitutional Court was useless for presidential election disputes," Fadli said. 

Instead, Prabowo's supporters are preparing to embark on mass protests in the streets on May 22, when the KPU is scheduled to announce the official result. Arief Poyuono, another Gerindra deputy chairman, went even further, with a call of civil disobedience, suggesting on Wednesday that Prabowo's supporters must stop paying taxes if Jokowi was re-elected.