Popular independent Ahn Cheol-soo is expected to mount strong challenge to the ruling New Frontier party candidate

This article is more than 8 years old

This article is more than 8 years old

The race for the South Korean presidency has opened up into a three-way contest after the millionaire software entrepreneur Ahn Cheol-soo declared his candidacy, ending months of speculation about a possible challenge to the country's political status quo.

Ahn, a popular independent who left business to become an academic and philanthropist, is expected to mount a strong challenge to the ruling New Frontier party candidate, Park Geun-hye, the daughter of a former South Korean dictator who at one point was expected to win comfortably.

Park, who won her party's endorsement last month, is aiming to become the country's first female president, more than 30 years after her father, Park Chung-hee, was assassinated by his own intelligence chief.

Ahn formed his anti-virus software company, Ahnlab, in 1995 and has promised to give up his remaining stake, worth a reported $324m (£200m), if elected.

He told supporters in Seoul he would create jobs for young people neglected by the current president, Lee Myung-bak, and tackle rising inequality in the world's 13th biggest economy.

"The people have expressed their hope for political reform through me. I want to become the person who puts that hope into practice," he said.

Recent opinion polls also show a sudden rise in support for Moon Jae-in, a human rights lawyer and chief of staff to former president Roh Moo-hyun who was nominated by the main opposition Democratic United party last weekend.

A poll conducted this week showed Moon ahead of Park for the first time, according to the Korea Times; he also defeated Ahn in a hypothetical two-way contest by a healthy margin, the paper reported.

Members of Moon's team told the Guardian as recently as last week that they believed Ahn would not run, leaving Moon as Park's sole challenger.

A poll earlier this month showed that in a three-way race, Ahn would receive 24.7% of the vote, with Park on 41% and Moon on 19.2%.

To avoid splitting the anti-conservative vote in the 19 December election and sending Park to the presidential Blue House, some expect Ahn and Moon to form an alliance, perhaps with one or the other agreeing to fill the less important role of prime minister.

On Tuesday, Ahn said it would be inappropriate to speculate about an alliance with Moon at this early stage in the contest.

Ahn's status as a political outsider has won him support among younger people and urban workers – the swing voters who could give him victory in December.

He has promised to take on the chaebol, the family conglomerates such as Hyundai and Samsung, that exert huge influence over the South Korean economy.

"I don't think we should be ambivalent about chaebol. We should introduce a 'corporate group law' to ensure they remain competitive but try to minimise their defects and abuses," he wrote in a book published earlier this month.

Despite his liberal domestic manifesto, Ahn said he would take a tough line against North Korea, with which relations have deteriorated rapidly since Lee was elected in 2007.

Ahn, 50, dismissed fears about his lack of political experience. "Some people ask what makes you think having run a small business prepares you to run an administration at a much bigger scale," he said in an interview last year.

"I just laugh when I hear people say that … I created something from nothing, I've overcome hardship."

Lee will not run in December's election as the South Korean constitution limits the presidency to a single five-year term.