Sam Rainsy this week handed additional evidence over to the courts which he says implicates Foreign Minister Hor Namhong in Khmer Rouge atrocities amid a growing legal battle that could see the opposition lawmaker stripped of his parliamentary immunity and investigated for defamation.

Namhong is suing Rainsy over comments alleging that Namhong oversaw activities at Boeung Trabek prison, a detention center for intellectuals and members of the royal family under Pol Pot’s regime.

“I have come here to reveal the truth with plenty of proof and evidence,” Rainsy said on July 9.

Rainsy claimed to have testimony from a Boeung Trabek survivor alleging that Namhong  had been appointed governor of Boeung Trabek prison and had overseen executions.

Namhong has repeatedly denied Rainsy’s accusations, claiming he was only as an ordinary prisoner. He could not be reached for comment.

The legal row has resulted in court officials requesting that the National Assembly “temporarily suspend the immunity of Sam Rainsy,” adding that it had collected enough evidence to warrant further investigation into Namhong’s defamation suit.

Cambodian lawmakers said they would consider request after the July 27 polls.