MANILA: The Philippines' election commission on Monday rejected a complaint seeking to block the presidential bid of the son of the late dictator Ferdinand Marcos, ruling prior tax violations while in public office should not derail his run.

The petition had sought to cancel the certificate of candidacy of Ferdinand Marcos Jr, accusing him of misrepresenting his eligibility because of the three-decade-old tax conviction and arguing it should mean a lifetime election ban.

But judges on the Commission on Elections (COMELEC) said the petition lacked merit.

"There is no intention on the part of respondent to deceive the electorate as to hide qualifications for public office," their ruling stated.

The petition filed by a group of civic leaders is one of a number of complaints designed to sideline Marcos, who has emerged as a clear favourite, centred on an 1995 conviction for failing to pay income tax and file tax returns while in public office from 1982-1985.

The Court of Appeals acquitted Marcos of non-payment of taxes in 1997, but it upheld the guilty verdict on failing to file tax returns, which the COMELEC noted "is not tax evasion".

In dismissing the petition, the COMELEC said there was nothing in the Court of Appeals' decision penalising Marcos, who has served as vice governor, governor, congressman and senator, with perpetual disqualification from holding public office.

That penalty, which was added as an amendment to the internal revenue code in 1985, only took effect in 1986 and therefore could not be applied retroactively, COMELEC added.

The lawyers in the complaint said they would file a motion for reconsideration with COMELEC's full bench of judges.

"We thank the Commission on Elections for upholding the law and the right of every bona fide candidate like Bongbong Marcos to run for public office free from any form of harassment and discrimination," Marcos's spokesman, Vic Rodriguez, said in a statement, referring to the candidate by his nickname.

The other petitions seeking to disqualify Marcos are pending with the COMELEC's first division.

The election to choose a successor to Rodrigo Duterte, who is barred by the constitution from a second term, takes place on May 9.

"The fact remains he (Marcos) is showing to be the most popular candidate," said political analyst Edmund Tayao, adding that "denying the public that choice will have serious repercussions".

Other leading candidates include senator and retired boxing champion Manny Pacquiao, Manila mayor Francisco Domagoso, Vice President Leni Robredo and Senator Panfilo Lacson, a former police chief.