Prime Minister Anwar Ibrahim has again refused to confirm or deny the existence of a royal addendum instructing authorities to allow Najib Razak to serve the remainder of his sentence at home, saying the directive could not be implemented due to the changing of the Yang di-Pertuan Agong.

"Why didn't we act? Because the Yang di-Pertuan Agong has been replaced. Any action we take must go back to the Yang di-Pertuan Agong," he said during a debate on an addendum attached to Najib's partial pardon earlier this year.

Earlier this year, the Pardons Board chaired by the then Agong, Sultan Abdullah Sultan Ahmad Shah, announced that Najib's prison sentence would be reduced to six years and his fine to RM50 million, which, if paid,would get him another year off.

However, his lawyer Muhammad Shafee Abdullah later accused the government of concealing an additional decree from Sultan Abdullah that Najib should serve the remainder of his sentence at home.

Sultan Abdullah, who ended his five-year term as Agong on Jan 30, was replaced by Johor's Sultan Ibrahim Sultan Iskandar.

Anwar said the royal addendum can only be released with the Agong's consent.

His response comes days after Najib's son, Nizar Najib, filed an affidavit containing a copy of the addendum signed by the sultan, stating that he was personally informed of it by the ruler himself.

The affidavit was filed on Dec 5 ahead of Najib's appeal against a High Court ruling that the existence of the addendum was hearsay.

In the Dewan Rakyat today, Kota Bharu MP Takiyuddin Hassan asked why the government had not disclosed the existence of the additional decree.

Anwar insisted that it could not be discussed publicly as it was the subject of a court case, adding that it also touched on the Agong's decision in the Pardons Board.

"Why has the government all along not told the truth about whether this amendment existed or not? Isn't this a lie and disobedience to an order of the Yang di-Pertuan Agong, and isn't it also considered by law as wrongful imprisonment, if there exists (the addendum), as it is a violation of the regulations?" he said.

"Honourable prime minister, the people of Malaysia demand clear explanation from you," said Takiyuddin.

In response, a visibly angry Anwar accused the opposition of hypocrisy for defending Najib, adding that they were interested in political mileage.

"As for the addendum, we cannot respond because the case involves the Yang di-Pertuan Agong and the Pardons Board, of which the Agong is the chairman. Since when are we allowed to talk about something that is pending in court?

"It's fine if you want to be a half-baked champion! But as for the law, please answer! Is a prime minister allowed to comment on the decision of the Agong in the Pardons Board?"

In July, the High Court dismissed as hearsay claims about the existence of the addendum, as contained in affidavits filed by Deputy Prime Minister Ahmad Zahid Hamidi and Pahang Menteri Besar Wan Rosdy Wan Ismail.