The ball is now in the hands of Shaun Abrahams and his National Prosecuting Authority (NPA), the Congress of the People (Cope) said on Friday.
"The NPA must stop acting like a protector and defender of a criminal suspect. They must uphold the values of the Constitution and the principles of the NPA legislation," said Cope's national chairperson Pakes Dikgetsi.
Dikgetsi was responding to a Supreme Court of Appeal (SCA) decision to dismiss the appeal brought by President Jacob Zuma and the National Prosecuting Authority, in relation to the reinstatement of corruption charges against the President.
The appeal was on Friday dismissed with costs.
Dikgetsi said Cope had always believed that there was a prima facie case of corruption which Zuma needed to answer to in a court of law.
"There can be no further prevarication or obfuscation about the way forward. The ball is now in the hands of Shaun Abrahams and his NPA," said Dikgetsi.
The party said it would closely monitor the conduct of the NPA to ensure that it executed its mandate without fear or favour.
The Supreme Court of Appeal in Bloemfontein handed down judgment in an appeal by Zuma and the NPA in the "spy tapes" saga.
Zuma and the NPA had approached the SCA seeking leave to appeal the 2016 decision by the North Gauteng High Court in Pretoria.
The 18 charges against Zuma were withdrawn in 2009, just before he was sworn in for his first term as President, but the Democratic Alliance (DA) wanted the charges to be reinstated.
In 2016, a full bench of judges overturned the NPA's decision to drop the corruption charges against Zuma that related to fraud, racketeering and money laundering.
Both the NPA and Zuma turned to the SCA after the High Court denied them direct access for an appeal.
But last month Zuma and the NPA made an about-turn and conceded that former national director of public prosecution Mokotedi Mpshe's decision not to prosecute Zuma, was irrational.