"If we are to fight corruption, culprits must be penalised and we must not let wrongdoing be swept under the rug," Justice Ministry permanent secretary Charan Phakdithanakul said.

Charan said he was poised to petition the National Counter Corruption Commission to launch proceedings against the two culprits involved.

"The culprits are two senior government officials who acted as brokers to offer bribes to Constitution Tribunal judges."

Charan said he had signed letters offering unspecified kickbacks.

One of the two was known as a "peddler of influence" who also allegedly sought to rig the verdict when three EC commissioners were tried last year for the botched April 2 poll. At that time, there was no physical evidence to link the alleged bribe to people involved but this time there was proof, he said.

The Judiciary Commission urged Charan to reveal the names of people involved to pave way for legal action, commission deputy secretary general Sarawut Benjathikul said. Supreme Court president Panya Thanomrod was concerned about the reputation of the courts and judges if the issue was left unresolved, Sarawut said.

Thai Rak Thai Group leader Chaturon Chaisang said authorities should prosecute the culprits but he "doubted" if Charan really had a case because of his "biased views toward the ousted government".