Democratic Party, right, and the main opposition People Power Party, left, submitting requests at the National Assembly's bills office in Seoul, Monday, calling for a parliamentary investigation into a shortage of ballots in the June 3 local elections. Yonhap

The rival parties each submitted a request Monday for a parliamentary investigation into an unprecedented shortage of ballots in last week's local elections, both calling for a thorough probe into what caused the incident but differing over its scope.

The ruling Democratic Party or Korea (DPK) and the main opposition People Power Party (PPP) separately filed their requests at the National Assembly's bills division but said they will hold follow-up discussions to narrow differences over details of the proposed probe.

The PPP proposed forming an 18-member special committee to oversee the probe for 60 days, with nine members from each of the rival parties and a PPP member chairing the committee.

Under the PPP's proposal, a special committee will look into the cause of the ballot shortage and whether it infringed upon voters' rights, as well as what the party described as violent police suppression during the removal of the ballot boxes from a polling station.