Libyan MPs voted on Sunday to ditch Prime Minister Mustafa Abushagur, extending the country's political stalemate.
Mr Abushagur was appointed on September 12 and had 25 days to form a cabinet. But MPs blocked his two attempts to do so, sparking the no-confidence vote.
He said he respected parliament's decision but warned them to replace him quickly "so the country does not slip into a vacuum."
Many MPs represent areas which have not been under the government's control since the overthrow of Muammar Gadaffi last year.
Warring militias which united against Gadaffi have since turned their guns on each other, making swathes of the country ungovernable, locking up thousands of supposed political opponents and pursuing their own agendas in spite of the government.
One group even bulldozed an ancient shrine in the capital Tripoli.
The country's slide into chaos was dramatically illustrated by the attack on the US consulate in Benghazi on September 11, which killed ambassador Chris Stephens.
Officials have since tried to rein in the militias. But a much-trumpeted chance to hand in weapons last week only drew a few hundred people out of an estimated 200,000 armed Libyans.
Over a thousand Libyans demonstrated in Tripoli yesterday for the end of a militia-run siege of Bani Walid, a town seen as a stronghold of Gadaffi supporters.