Shah Alam: Malaysia's veteran ex-leader Mahathir Mohamad was named as the opposition's prime ministerial candidate today as a bruising election battle looms against scandal-plagued premier Najib Razak and his long-ruling coalition.

The decision means the 92-year-old, a hugely divisive figure criticised for ruling with an iron fist during his long reign, could return as premier 15 years after stepping down.

But he also agreed to make way for jailed opposition leader Anwar Ibrahim -- his former nemesis turned political ally -- to become prime minister on his release from prison if Anwar is granted a royal pardon.

Mahathir's ascent to opposition prime ministerial candidate is the latest sign of how dramatically Malaysia's political landscape has been shaken up by a massive financial scandal that has rocked Najib's government.

Mahathir came out of retirement to take on Najib as anger mounted at allegations billions of dollars were looted from a state investment fund, 1MDB, founded by the current premier.

Both Najib, whose United Malays National Organisation (UMNO) has led the country in a coalition since independence in 1957, and the fund deny any wrongdoing.

The elections must be called by August but speculation is mounting they will be held in the next few months.

The decision to pick Mahathir as candidate for premier was endorsed by senior leaders of four-party coalition Pact of Hope at their convention in Shah Alam, just outside Kuala Lumpur, to rousing cheers by hundreds of supporters.

"Our great focus is to save our beloved country," Mahathir, who ruled the country for 22 years at the head of the UMNO, said in a speech.

"It wasn't easy for the parties that were my enemies before to accept me -- but they are aware of the importance of bringing down the current government."

People's Justice Party president Wan Azizah Wan Ismail, Anwar's wife, was named as deputy prime minister candidate.

The coalition will be hoping that Mahathir, who has set up his own party to take on Najib, will be able to attract votes of from Muslim Malays, who make up about 60 per cent of the population.

But most analysts think that the ruling coalition will win as the system is greatly stacked in their favour, the economy has performed well recently and the opposition has often appeared disunited.

Anwar, jailed after being convicted of sodomy, will be released on June 8, reports said today, but he will be barred from politics for five years unless granted a royal pardon.