Former journalist and rights activist Dullas Alahapperuma is an unlikely contender to be Sri Lanka's leader, but is the main challenger to the current acting president in a parliamentary vote Wednesday.

The 63-year-old former media minister secured the support of the main political opposition on Tuesday, after promising to unite a fractured, crisis-hit nation following Gotabaya Rajapaksa's resignation last week.

"It is a crime not to do anything while the country is rapidly going down," Alahapperuma told AFP while Rajapaksa was still in office.

"We must get the country out of this mess. Otherwise we won't have a country very soon."

Sri Lankan politics has been dominated for decades by a series of family dynasties, but Alahapperuma's family never had those connections.

Both his parents were schoolteachers, and he began his career as a reporter for Lakmina, a local newspaper in Colombo.

Moving into leftist activism, he published his own political tabloid, the "Dullas News".

That propelled him to a provincial council seat in 1993, and a year later he became a member of parliament.

He worked closely at the time with Mahinda Rajapaksa, who was campaigning against rights abuses by the government of then-president Ranasinghe Premadasa.

Rajapaksa and his family went on to dominate Sri Lankan politics for years -- the recently ousted president is his younger brother -- and several members of the clan were themselves accused of rights abuses in the country's fight against a Tamil rebellion.

In an illustration of the dynastic nature of Sri Lankan politics, it was Premadasa's son Sajith, now the leader of the opposition in parliament, who nominated Alahapperuma for the presidency on Tuesday.

Dullas Alahapperuma held three different positions in the government of Gotabaya Rajapaksa, but was also an outspoken critic of the former president in recent months
Dullas Alahapperuma held three different positions in the government of Gotabaya Rajapaksa, but was also an outspoken critic of the former president in recent months AFP / Ishara S. KODIKARA

Alahapperuma left politics in 2001 to pursue higher education at the University of Iowa, but re-entered parliament in 2005 when his ally Mahinda became president.

Most recently, he held three different positions in Gotabaya's cabinet.

On his first day as energy minister, there was a nationwide blackout.

As media minister, he maintained close ties with journalists and was seen as an unabrasive spokesman for the cabinet -- unlike several of his predecessors.

As public anger grew against the Rajapaksa clan over the country's worsening economic crisis, Alahapperuma publicly urged the president to form a unity government earlier this year.

He accused the Rajapaksa administration of unleashing attacks against dissident journalists and activists, and admitted that he was powerless to contain the oppression.

He was seen as an outspoken critic within the cabinet, a record that may have helped him secure the opposition's support for his candidacy for president.

A father of two sons aged 27 and 26, Alahapperuma is married to a popular film actress, Pradeepa Dharmadasa.

If he wins on Wednesday he has promised to make opposition leader Premadasa his prime minister in what he calls the country's first "consensual government".

The former cabinet minister wants to "put an end to the deceitful political culture, that clouded our nation for ages", he tweeted on Saturday.