KUALA LUMPUR - Former Malaysian prime minister Mahathir Mohamad on Saturday explicitly told Umno to remove Mr Najib Razak, saying he was an incompetent prime minister who could not explain how the country's state fund lost money.

Dr Mahathir said he did not blame Mr Najib for the failure of the crooked bridge project but the latter must account for the money lost by 1Malaysia Development Berhad (1MDB).

"We are faced with this choice: either you remove a prime minister who has failed and who will lead Umno to lose the next election, or you take your chance that if he goes off, we may be able to revive Umno," the Malaysian Insider quoted Dr Mahathir as telling reporters after speaking at an international forum on criminalising war.

"I wrote about 1MDB but people say 'Oh, he is unhappy not with 1MDB but with the crooked bridge. I don't advocate the removal of a prime minister because he is too afraid of Singapore to build a crooked bridge.

"I am sympathetic towards him because he is very weak so he cannot build the bridge brick by brick,'' Dr Mahathir was quoted as saying.

"So for that I excuse him, but when you lose money and cannot explain where the money is, I think you are not competent to become PM," he added.

Mr Najib has faced increasing pressure in the past six months, including from Umno hardliners, some of whom had gravitated towards Dr Mahathir, who was prime minister for 22 years.

In a special interview with TV3 last week, Mr Najib said Dr Mahathir's attacks against him could have been triggered by their disagreement on the crooked bridge and the 1Malaysia People's Aid (BR1M) cash handouts.

Dr Mahathir first mooted replacing the Causeway with a bridge in 2001 to ease traffic congestion, allow stagnant water to flow and improve the marine environment, as well as to allow ships to sail across the Johor Strait - which would be a major boost for Johor's two ports.

But to Singapore, the project would incur huge financial costs without bringing significant benefits.

This led Dr Mahathir to announce in 2003, just before stepping down, that Malaysia would go ahead with a crooked bridge if Singapore refused to demolish its half of the Causeway.

The bridge envisioned is a six-lane S-shaped highway that would curve in such a way that it would allow vessels to pass under it.

Dr Mahathir also disapproved of the BR1M initiative, saying it would make people become dependent on handouts.