"We found there was abuse of power, ranging from legal aspects to the use of state facilities," PDIP Secretary General Hasto Kristiyanto told Reuters, without providing specifics or evidence to support the allegation.
PDIP backed Ganjar Pranowo for the presidency, who finished a distant third behind Defence Minister Prabowo Subianto, the clear winner according to unofficial vote tallies and an ongoing preliminary count by the poll body.
The presidential palace did not immediately respond to a request for comment on the allegations or the planned investigation.
Despite various accusations by parties, none have provided specifics or details of the scale of the alleged violations. Independent poll monitors have so far given no indication of irregularities significant enough to impact the outcome.
Though the Constitutional Court typically handles election disputes, Indonesia's parliament has the power to conduct investigations on government policy or implementation of certain regulations and can examine the conduct of public officials, including the president.
Hasto said the probe aimed to safeguard democracy and draw public attention to the alleged wrongdoing.
"If we did not do this comprehensive correction, then what's the point of having an election in the future?" he said, adding it does not aim to impeach President Joko Widodo, better known as Jokowi.
For parliament to launch a probe, the plan must be proposed by at least 25 lawmakers and more than one party and be approved by more than half of legislators present at a plenary session.
PDIP's plan is backed by another party but would need support from those who endorsed second-place finisher, Anies Baswedan.
Prabowo looks to have swept the Feb. 14 election with almost 60% of the votes, boosted by the tacit backing of Jokowi, who has faced mounting allegations of ethical breaches and meddling, which his allies deny.
Prabowo also ran on a ticket with Jokowi's son, owing to a last-minute decision by the Constitutional Court, headed by the president's brother-in-law, to change election eligibility rules.
Hasto said PDIP and other backers of Ganjar would file a case concerning the alleged electoral violations with the same court, but gave no timeframe.
On Friday, three parties behind Anies said they would support a PDIP-led probe. Parties backing Anies and Ganjar if combined would constitute a majority, with 314 of 575 seats.
