Vowing to fight against corruption that pervades the impoverished Southeast Asian nation, Benigno Aquino said he would be a leader for all sectors of society and not just the rich.

"I will be there because of the people, I will stay there because of the people and hopefully I will be true to my word to serve the people," Aquino, 49, told a crowd of cheering supporters as he declared his presidential bid.

Aquino made the announcement at Manila's historic Club Filipino, where his mother "Cory" was sworn in as president in 1986 after leading the "people power" revolution that ended dictator Ferdinand Marcos's 20-year reign.

Aquino will represent the opposition Liberal Party in next year's elections, hoping to end the reign of President Gloria Arroyo's ruling coalition.

The Liberal Party has been a fierce critic of Arroyo, who is mandated by the constitution to step down, alleging widespread corruption in her administration.

Arroyo's spokesman Lorelei Fajardo conceded Aquino has emerged a strong contender for the presidency, while calling him a "welcome addition to the race."

Aquino said he would rely on the help of ordinary Filipinos to become president, just as they propelled his mother to power.

"The reason why I am on this path is because I believe the public will support and help me in the campaign," he said.

"I want to make democracy work not just for the rich and the well-connected, but for everybody."

He also promised to give the nation "closure" by going after stolen wealth controlled by the Marcos family.

Although Aquino has been a member of parliament for 11 years, he said he only began seriously considering a presidential bid after seeing the massive outpouring of support following his mother's death from cancer last month.

His father, also named Benigno, is held in equally high esteem by many throughout the nation of 92 million people.

Marcos' gunmen shot him dead at Manila airport in 1983 as he returned from exile.

His assassination led to Cory reluctantly moving into politics and becoming president for six years, a period that has been widely acclaimed for restoring democracy after a generation of martial law.

Aquino called on Filipinos to recall his mother's achievements when they considered who they wanted to be their next president.

"During my mother's time, she was not corrupt. Even the policeman on the street had second thoughts of being corrupt," he said.

Nevertheless, his family belongs to one of the powerful clans that have dominated Philippine life for generations, and observers have pointed out that a win for Aquino would be another victory for the elite.

Corazon Aquino was born into the Cojuangco family, which continues to play a major role in the economy.

Her cousin, Eduardo Cojuangco, is majority owner of brewing giant San Miguel and, according to the latest Forbes rich list, the seventh wealthiest man in the Philippines.

Aquino's decision also opens the tantalizing prospect of a two-way race for the presidency against his first cousin, Gilberto Teodoro, who is a leading candidate to run for the ruling coalition.

The first challenge for Aquino, known by his nickname of "Noynoy," is to unite a fractious opposition.

Former president and movie star Joseph Estrada wants to run again, while property tycoon Senator Manuel Villar has been leading recent polls of potential opposition presidential candidates.