The verdict comes a week ahead of national elections and a day after Khan was sentenced to 10 years in prison in a case related to leaking state secrets.
The court disqualified Khan from holding any public office for several years.
Khan's lawyer Babar Awan said Khan was convicted so swiftly that the judge did not wait for the arrival of his legal team.
Awan said Khan's basic human and fundamental rights had been violated, and the defense would challenge the latest conviction and sentencing.
