Barak Sope, Vanuatu's former prime minister who was recently pardoned of fraud charges, has been barred from parliament after trying to attend the debate on the budget.
Police were called to escort him from Parliament after he tried to reclaim his seat.
Mr Sope, who had been jailed for three years in July for signing controversial bank guarantees with seeking Parliament's approval, was given a full pardon last month the President.
But Mr Sope had claimed he should be allowed to resume his seat, but the State law office says he has lost it because of the conviction and the failure to appeal within 30 days of that ruling.
A by-election is likely early next year.
The Opposition leader Willie Jimmy has said none of the other Opposition parties would stand candidates against Mr Sope.