Ahmed Maiteeq could be forced to step down as Libya’s prime minister, just days after taking office.
According to a Supreme Court official, his election to the post contravenes Libya’s temporary constitution.
His lawyer has appealed the decision and declared the vote legitimate.
Maiteeq was elected following a chaotic vote, which has been disputed by some politicians.
Outgoing Prime Minister Abdullah al-Thinni is among them.
Further opposition comes from supporters of dissident General Khalifa Haftar, who launched a military operation against terrorists in Benghazi.
The General was recently the target of a rocket attack on a government building in the capital Tripoli.
Nearly three years after Muammar Gaddafi was overthrown, officials are still struggling to restore order in Libya.
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