A senior Libyan parliamentary official says the assembly does not recognise the country's new prime minister, Ahmed Miitig.
Ezzedin Al-Awami, the first vice-president of the parliament, said in the confusion of a vote taken by parliament, Miitig failed to get the number of votes required on Sunday.
A statement posted on the government website said Miitig, an Islamist-backed businessman, received 113 votes but needed 120 to be declared the country's new prime minister.
In a second statement published on the website, Awami says the vote was "void and illegal".
It followed an earlier chaotic session of the General National Congress (GNC).
Miitig, 42, was initially reported to have mustered only 113 votes of 120 votes needed under the constitution in a vote of confidence.
But GNC official Salah al-Makhzoum later said Miitig had in fact clinched 121 votes in the 185-seat interim parliament, apparently after a recount, after beating off challenger Omar al-Hassi, a university professor.
Some deputies denounced the recount, which they said took place after the session had officially closed.
"What is happening is illegal," said GNC spokesman Omar Hmidan.
The voting had been broadcast live on state television.
