Ezziddine Awami, first vice president of the General National Congress (GNC), declared invalid a vote earlier in the day that elected Ahmed Maitiq as prime minister, Xinhua reported.
The election of Maitiq, a 42-year-old businessman, was announced Sunday afternoon by Second Deputy Secretary of GNC Saleh Makhzoom.
The interim cabinet, in a statement issued after Makhzoom's announcement, also rejected Maitiq's election as invalid.
Meanwhile, Libya's acting Prime Minister Abdullah al-Thinni's spokesperson Ahmad Lamen confirmed in a press release that the Thinni cabinet will stay on until a new round of election is held.
Lamen said the cabinet will "abide by the constitution" and "fully implement the absolute legitimate power".
During the earlier vote, Maitiq only got 113 votes at first, falling short of the 120 quorum, but after a short break of the chaotic session, he got eight more additional votes.
The political deadlock facing the North African country followed the 2011 uprising which toppled former leader Muammar Gaddafi. Libya's weak central government has not been able to establish effective control of the whole country, making the oil- rich nation an arena for militias, extremists and international powers.