By Joseph Sipalan
KUALA LUMPUR (Reuters) - Malaysia's ruling party on Friday voted to suspend its deputy president, months after he was sacked from his job of deputy prime minister for openly questioning Prime Minister Najib Razak over a financial scandal involving a state-owned firm.
The move tightens Najib's grip over his United Malays National Organisation (UMNO), and weakens rival factions that demanded he step down over debt-laden state fund 1Malaysia Development Berhad (1MDB) and a donation of $681 million.
Najib, the president of UMNO, has been buffeted for months by allegations of graft at 1MDB and revelations of the transfer of funds, adding to a sense of crisis in a country under economic duress from slumping oil prices and a sliding currency.
On Friday, UMNO's supreme council, the party's top decision-making body, suspended Muhyiddin Yassin from all his duties as deputy president until the next party polls in 2018.
"The deputy president's role in the constitution is to help the president," UMNO secretary-general Tengku Adnan Tengku Mansor told a news conference.
"His behavior did not reflect that of a deputy president, to help the president strengthen the party. He had also undermined the party."
A spokesman for Muhyiddin said there was no immediate comment but he would issue a statement soon.
Muhyiddin, along with former premier Mahathir Mohamad, has been one of the fiercest critics of Najib over his alleged involvement in the 1MDB scandal.
This week, Malaysia's anti-graft agency said an external review panel had asked it to continue investigations into the transfer into Najib's personal bank account, despite an order by the country's top lawyer to close the case.
Najib has denied any wrongdoing, saying the funds were a political donation and he did not take any money for personal gain. The scandal was "an unnecessary distraction", he said, after being cleared by Attorney-General Mohamed Apandi Ali last month.
Najib sacked Muhyiddin as deputy prime minister in August, along with several other cabinet members.
Najib removed Attorney-General Abdul Gani Patail, who set up a special task force to investigate 1MDB. His loyalists also forced Mahathir's son out of his post as chief minister of the northern state of Kedah.
But the prime minister faces renewed pressure after international investigators said they had grounds to probe 1MDB for corruption.
Party vice-president Ahmad Zahid Hamidi will stand in for Muhyiddin, Tengku Adnan said. He added that Najib and Ahmad Zahid excused themselves from the discussion on the suspension of Muhyiddin, who did not attend the meeting.
(Writing by Praveen Menon; Editing by Clarence Fernandez)