JAKARTA, Feb. 1 (Reuters) - Indonesian President Joko Widodo is facing mounting public criticism over his perceived political interference and lack of neutrality as he campaigns for the leading candidate in this month's presidential election.

While Jokowi, as the president is known, has not explicitly endorsed any of the three candidates in the Feb. 14 election, he has made highly-publicised appearances with frontrunner Prabowo Subianto, who is running with the leader's son as his candidate for vice president.

In Indonesia, sitting presidents are allowed to campaign for candidates provided they do not use state resources and take official leave to do so, but incumbents have typically remained neutral.

But since October, when a top court tweaked eligibility rules to allow Jokowi's 36-year-old son to run with Defence Minister Prabowo, the president has faced mounting allegations of ethical and legal breaches.

The furore has prompted Jokowi to repeatedly clarify his stance and even show reporters print-outs of the election law to clear his name.
"Yes, a president can join the campaign. Yes, a president can pick a side. All that is permitted as long as he does not use state facilities," he told reporters last week, after attending a defence event with Prabowo.

Critics say he has flouted election laws by appearing to campaign for Prabowo while attending government functions and meals together, and rival candidates allege state agencies have disrupted rallies and torn down promotional materials on the campaign trail.

"Some of our campaign activities were indeed cancelled or not permitted by various local governments...and non-governmental entities, which likely were influenced by those in power," said Ade Chandra, a campaign spokesperson for rival presidential candidate Anies Baswedan.

State rice handouts have allegedly included Prabowo campaign stickers, prompting complaints from rivals, according to media. The government has denied that any one candidate benefits from the state social assistance programme.

Discontent with Jokowi's actions is also extending to his cabinet, from which chief security minister Mahfud MD, who is a vice presidential candidate on a rival ticket, has said he will resign soon.

A group of academics at Jokowi's alma mater, Yogyakarta's Gadjah Mada University, have issued a petition highlighting the president's "disregard for political principles", and urging him to "return to the democratic path".

Nearly 205 million voters are registered to vote in the world's third-largest democracy for a successor to Jokowi, who has spent a decade in office and is limited to two terms by the constitution.

With a 20-point lead in opinion surveys, 72-year-old Prabowo is the clear favourite, an advantage analysts say is driven largely by the president's backing.