It is normal practice for Prime Minister Najib Abdul Razak to sign off on documents presented to him, said Tourism and Culture Minister Nazri Abdul Aziz.

The Umno supreme council member pointed out that he does it himself when his officers hand him documents.

"When we're asked to sign documents, we sign it. I myself as a minister, my chief executive chair many meetings. So when (a document) comes to me, I sign it.

"Why wouldn't I trust my chief executive?" he told a press conference in Putrajaya today.

He said this when asked to comment on whether Najib should be implicated in the 1MDB scandal since his signatures are on company documents.

Article 117 of 1MDB's Memorandum and Articles of Association (M&A) requires the prime minister to approve major decisions, including financial transactions.

Nazri, however, said the prime minister had no time to micro-manage 1MDB.

"To say that Najib micro manages 1MDB and made day-to-day decisions is not accurate. He has other things to do," he added.

Najib, as chairperson of the board of advisers, reportedly signed off on the joint-venture agreement with PetroSaudi International, where 1MDB invested US$1 billion.

This is according to former 1MDB CEO Shahrol Azral Halmi's testimony to the Public Accounts Committee.

He said 1MDB obtained the shareholders' and board approval for the deal through the document signed by the prime minister, in accordance with the company's memorandum and article (M&A).

Article 117(c) of the M&A states that any financial commitments, restructuring or anything to do with the government guarantee – for the interest of the company, country or government policy – must require the prime minister's written approval.

The joint venture was signed without the management first fulfilling the requirements set by the 1MDB board, including an independent valuation of the oil fields PetroSaudi was putting up as its part of the venture.