Azimio coalition has gone to court to stop a commission of inquiry into the Shakahola tragedy, arguing that the move is unconstitutional.
In a petition filed at the High Court, the coalition says President William Ruto's appointment of the eight-member team is illegal and amounts to a usurpation of powers vested in other state organs by the Constitution.
The opposition coalition also says Dr Ruto is empowering his personal nominees to undermine the constitutional mandate and authority of constitutional institutions and state organs.
Dr Ruto last week appointed the commission, chaired by Court of Appeal judge Jessie Lesiit, to investigate the deaths, torture, inhuman and degrading treatment of victims linked to the Good News International Church in Kilifi.
The commission is expected to establish the circumstances under which the deaths, torture and inhuman and degrading treatment took place.
But Azimio La Umoja argues that the commission of inquiry, which is due to be sworn in later today, was appointed in contravention of the constitution.
"The petitioner states that the action of the 1st respondent in constituting the Commission of Inquiry interferes with the independence of the Judiciary under Article 161 of the Constitution of Kenya which provides that 'in the exercise of judicial authority, the Judiciary shall be subject only to this Constitution and the law and shall not be subject to the control or direction of any person or authority'." The petition was filed by lawyer Paul Mwangi.
Mr Mwangi says Parliament can establish a subordinate court or an independent tribunal by an Act of Parliament and the Judiciary is empowered by the Constitution to recruit qualified persons to serve in the courts.
The petition goes on to say that the appointment of Justice Lesiit as chairperson of the commission exposes the judiciary to embarrassment because it was made without consultation with Chief Justice Martha Koome and the judge will work under the supervision and jurisdiction of the High Court.
Furthermore, Azimio argues, Justice Lesiit will work under the direction of the President, who will determine her remuneration and allowances, and will have to compromise her independence.
"The precedent that will be set by not declaring the Commissions of Inquiry Act unconstitutional is that the President will now and in the future be able to entice sitting judges of the judiciary with appointments to commissions of inquiry and other executive appointments and thereby influence judges with perks that will create bias in such judges when they sit in judgement on actions of the executive in cases that come before them," Mwangi said.