"It wasn't an easy decision to make but after a great deal of consideration I felt it was the right one for me and it's time to hand it over to the next generation," he said.
The Opportunities Party received 2.22 per cent of the general vote in October's election, not enough for the five per cent threshold to enter Parliament.
Manji was also bidding for the Christchurch seat of Ilam however came second behind National candidate Hamish Campbell by 7800 votes.
Manji said despite not being successful, the party still made a positive impression with over 63,000 votes.
"I have been fortunate to have a fantastic core team and it has been a pleasure to also work with so many committed volunteers and supporters."
He said the party will hold a meeting early next year to discuss its future.