Lawyer Mohd Haniff Khatri Abdulla has challenged the new Malaysian Anti-Corruption Commission head Dzulkifli Ahmad to re-open the probe on Prime Minister Najib Abdul Razak.

This follows Dzulkifli's emotional speech on Tuesday, where he warned political leaders not to betray the people's trust and also advised judges to show courage.

Mohd Haniff, who is a lawyer to Dr Mahathir Mohamad, said Dzulkifli should follow his own advice and re-open investigations against Najib, in light of the US Department of Justice civil forfeiture suit relating to 1MDB.

"If you are sincere in what you said two days ago, then I challenge you to follow your advice and ask the Attorney-General's Chambers to allow the MACC to re-open the investigations on Najib, in relation to corruption, criminal breach of trust or abuse of power related to 1MDB.

"Also I challenge the MACC under your leadership to seek mutual legal assistance to facilitate the commission in the gathering of information from the US DOJ or the Federal Bureau of Investigations,” said Mohd Haniff on his Facebook page.

Mohd Haniff said there were no laws that could allow the attorney-general to prohibit the case from being re-opened.

He said that the US DOJ's court filings were reasonable cause for the re-opening of investigations and that the AG's Chambers, as a professional and responsible institution, should do so in light of new evidence.

Previously, the MACC under then chief commissioner Abu Kassim Mohamed had applied twice for MLA, but the request was turned down by the AG's Chambers, under the helm of Mohamad Apandi Ali.

Eventually, the MACC's investigation papers were submitted to the AG's Chambers in December. A month later, Mohamad Apandi declared that there was no case against Najib and ordered for investigations to cease.