The Abuja Division of the Court of Appeal has sacked Ishaku Abbo, the lawmaker representing Adamawa North Senatorial District in the National Assembly.
Mr Abbo, a member of the All Progressives Congress (APC), confirmed to Channels Television that his victory was invalidated on Monday.
It is not clear whether the last has been heard of the legal battle which could drag along up to the Supreme Court.
Mr Abbo was declared the winner of the March 25 senatorial election after scoring 71,927 votes while the Peoples Democratic Party candidate, Yohanna Amos, scored 61,895 votes to come second, thus returning him to the Red Chamber.
The PDP is celebrating the victory as a major win as it would boost their quest for legislative influence.