Former Malaysian prime minister Mahathir Mohamad has resigned from his position as chairman of Proton Holdings and chairman of the company's UK sports car subsidiary Group Lotus.

Proton Holdings is now a subsidiary of one of Malaysia's largest diversified local conglomerates, DRB-Hicom, which acquired majority control from state-controlled companies in 2012.

Mahatir also resigned from leading positions at University Teknologi Petronas, the Langkawi Development Authority and the Tioman Island Development Authority. In early March, he was dismissed as advisor to state-owned oil company Petronas after he resigned from the government's political party UMNO at the end of February. 

The 90-year old feels he can no longer hold positions in government-related organisations as he continues his opposition to current prime minister Datuk Seri Najib Tun Razak over allegations of irregular financial payments.

Proton thanked Mahathir for his contributions to the company, not only in his capacity as chairman in recent years but also for his role in the establishment of Proton in the mid-1980s and his support for its development over the years.

Mahatir was one of Asia's longest-serving government leaders, having held the post of prime minister for 22 years – between 1981 and 2003.