Libya's Supreme Court Thursday ruled that the election of new Prime Minister Ahmed Maitiq was illegal, according to court officials.
Maitiq, a businessman from Libya's third largest city of Misrata, was sworn in as prime minister last month, but he was immediately challenged by his predecessor Abdullah Thinni and some judicial officials.
Thinni has till now refused to transfer power, although forces allegedly loyal to Maitiq have occupied the government compound, Xinhua reported.
Some judicial officials said the earlier parliamentary confidence vote which confirmed Maitiq as the new prime minister was invalid because less than half of the lawmakers, mostly Maitiq backers, attended the session.
The Libyan parliament has been stuck in a deadlock between the secular groups and Islamists since the 2011 protests that toppled the country's former leader Muammar Gaddafi.
Some analysts said the ruling might set the stage for a more intense power struggle between different groups.