Lawmakers demanded Thinni submit a new cabinet with not more than 10 ministers, Faraj Hashim said. Thinni had on Wednesday presented a cabinet with 16 ministers.
Thinni, a former career soldier, has been the oil producer's acting prime minister since March. He stood down after June elections and the new parliament reappointed him at the start of this month.
His administration has failed to impose order on a fragmenting country, and many observers fear Libya is heading for civil war.
Armed militias and Islamists who backed the rebellion to overthrow Muammar Gaddafi in 2011 have kept their weapons, staking claims to territory, oil and other resources.
An armed group from the western city of Misrata seized the capital Tripoli in August and forced the elected parliament to move to the east of the country. The Misrata group has set up its own parliament and government, which are not internationally recognized.
REUTERS