TUNIS, Oct 30 (Reuters) - The United Nations Libya mission said on Saturday that the country"s parliament should amend its election law to hold both presidential and parliamentary elections on Dec. 24 as originally envisioned in a peace plan. The House of Representatives (HoR), Libya"s eastern-based parliament, has issued separate laws for a presidential election on Dec. 24 and a parliamentary election that would be held at a later, unspecified, date. Wrangling over the elections, planned as part of a wider peace push that has also brought a transitional unity government into office, has threatened to derail Libya"s efforts to end a decade of chaos and violence. Critics of the HoR, as well as rival Libyan political institutions, have denounced its election laws as being intended to preserve the power of the chamber"s leadership. Others have accused those critics of seeking to delay or divert the election. "Respecting the principle of simultaneous presidential and parliamentary elections on 24 December 2021 is needed to preserve the integrity of the electoral process," said UNSMIL, the U.N. Libya mission. It said simultaneous elections on that date were also needed to ensure the credibility of the nationwide vote and acceptance of its results. It also urged an amendment to allow candidates who already hold public office to be able to suspend their duties to be able to compete in the election. Libya has had little peace or stability since the 2011 NATO-backed uprising against Muammar Gaddafi. It split in 2014 between warring eastern and western camps with rival administrations based in each region. The latest peace push follows the collapse last year of an offensive by eastern commander Khalifa Haftar on the capital Tripoli. A ceasefire has held since then though some of its provisions remain unmet.