Umno is planning to totally deny its deputy president Muhyiddin Yassin a platform to speak to its members at the party's annual assembly next week, as Prime Minister Najib Razak moved to tamp down a possible revolt.

The format of the closely watched five-day assembly is being changed for the first time in decades, with Umno secretary-general Tengku Adnan Tengku Mansor telling a media briefing yesterday that he did not expect any "fireworks".

The ruling party's supreme council led by Datuk Seri Najib will make a final decision next week whether to disallow Tan Sri Muhyiddin from giving a traditional winding-up speech at the end of the assembly, Datuk Seri Tengku Adnan said.

"In my view, only the president (Mr Najib) will speak," he said, echoing the current popular view in Umno's leadership and its band of online bloggers.

Malaysia's biggest political party is deviating from longstanding traditions this year as party president Mr Najib and his supporters worry that giving Mr Muhyiddin a speaking platform will give dissenters a stronger voice.

Mr Muhyiddin was sacked as deputy prime minister in August after he questioned Mr Najib on debt-laden state investment firm 1Malaysia Development Berhad and the source of nearly US$700 million (S$987 million) found in the personal bank accounts of the Prime Minister.

Mr Muhyiddin might raise the same issues if given a platform.

Umno has already stopped him from giving a speech at the joint opening of Umno's three wings, Women, Youth and Puteri. The Umno deputy president traditionally speaks at this meeting.

He should, also in accordance with tradition, at the end of the five-day meeting, join the party president, three wing chiefs and three vice-presidents in giving winding-up speeches to acknowledge the multiple concerns voiced by the delegates.

This year, 2,762 delegates are attending the main assembly, with several thousand more registered as observers.

There are other changes.

Umno's annual assembly typically starts on a Tuesday evening with the joint wing meeting. But this year, the opening will happen only a day later, Mr Tengku Adnan said.