KUALA LUMPUR — Dr Mahathir Mohamad is celebrating his 90th birthday today (July 10) and Malaysia’s longest-serving prime minister remains sharp and combative as ever, as he continues campaigning to oust his latest successor Najib Razak.

Dr Mahathir, who was prime minister from July 16, 1981 to October 31, 2003, was born in Alor Star, Kedah on July 10, 1925 but his official birthdate is December 20.

It is understood that a big birthday bash has been organised for the medically trained politician this month.

But age has not slowed him down despite stepping down from public office in 2003. Dr Mahathir remains a key influential figure in Malaysian politics – who helped remove his successor Abdullah Badawi in office in 2009 and now agitating for Mr Najib’s ouster because of the scandals surrounding strategic investor 1Malaysia Development Bhd (1MDB).

The influential politician had cut his support for Mr Najib in August 2014 and in recent months, has ratcheted his campaign against the prime minister, whose father, the late Abdul Razak Hussein, was also prime minister.

He had also asked Mr Najib to resign from the top job, echoing the calls of both government and opposition leaders who are seeking the truth behind The Wall Street Journal’s (WSJ) revelations last week that US$700 million (S$944 million) had been funnelled into Mr Najib’s bank accounts.

The prime minister has vowed to fight the WSJ claims, saying he did not gain personally from the accounts in AmPrivate Bank. Bank Negara Malaysia has frozen six bank accounts but said none was linked to the prime minister.

Despite that, Dr Mahathir has been asking the authorities, including the Internal Revenue Board, to investigate Mr Najib’s wealth and harangue the government to explain the high debt racked by 1MDB.

The auditor-general and Public Accounts Committee (PAC) are investigating 1MDB’s business but an interim report submitted yesterday had cleared the company of any wrongdoing.

But Dr Mahathir has cleared through the fog surrounding 1MDB to ask one question: why did 1MDB raise that much debt but only spent US$15 billion to acquire land and utilities across Malaysia and Asia.

Mr Najib last week accused his former political mentor of working with the foreign media against him after several exposes in WSJ and The New York Times.

Dr Mahathir has denied the claims but remains a formidable political influence among the 30-million population, most of whom grew up during his rule. THE MALAYSIAN INSIDER