With the exception of Brunei's sultan Hassanal Bolkiah who succeeded his father in 1967, the 72-year-old Mahathir is the longest serving leader in the Association of southeast asian nations (asean), with 17 years at the helm.

Singapore's former prime minister Lee Kuan Yew, asean's elder statesman, is two years older than Mahathir but has been in semi-retirement since handing over power to Goh Chok Tong in 1990.

While the outspoken Malaysian leader is no stranger to controversy, he had been particularly prominent since the asian economic crisis erupted in July last year, repeatedly blaming outsiders for the region's problems.

Only a week before the Indonesian president stood down, Mahathir was once again pointing the finger at unidentified foreigners, this time for allegedly trying tounseat both him and Suharto.

"He was playing an effective role even when suharto was around. I suspect his impact will be greater with the Indonesian leader leaving the scene," said Chandra Muzaffar, a former politics professor who now heads a Malaysian group known as international movement for a just world.

A regional diplomat said Suharto's departure may give prime minister Mahathir "more room to manoeuvre" within Asean.