Bayelsa State Gubernatorial Petition Tribunal has sacked Governor Douye Diri.
It ordered the Independent National Electoral Commission (INEC) to conduct a fresh election within 90 days.
His election was nullified based on a petition by the Advanced Nigeria Democratic Party (ANDP).
The party argued that it was unlawfully excluded from participating in the poll.
The ruling comes 48 hours after the tribunal dismissed three other petitions.
They were filed by the Alliance for Democracy (AD), the United People’s Congress (UPC) and the Liberation Movement (LM).
However, Diri of the People’s Democratic Party (PDP) can appeal the latest judgment.
