Deputy Home Minister Nur Jazlan Mohamed said that police are piling up more evidence to build a more serious case against former prime minister Dr Mahathir Mohamad.

"No, we will not stop him (from talking); now we let him talk and talk. Maybe police want to pile more evidence to bring more serious charges against Mahathir," said Nur Jazlan when asked if authorities will do anything to stop Mahathir's constant criticism.

He said that the police would only take action against the former Umno veteran when they are satisfied that their prosecution of the case will be successfully proven in court.