OKLAHOMA CITY (AP) — The Oklahoma Supreme Court has tossed another revenue bill passed by the Legislature as unconstitutional, making the state's current budget hole about $500,000 deeper.

In a 6-3 decision on Tuesday, the court ruled the new registration fees of $100 for electric and $30 for hybrid vehicles was unconstitutional.

The new fee was expected to generate about $500,000 for the current fiscal year and $1 million annually when fully implemented, with the money earmarked for road maintenance.

The Oklahoma Sierra Club challenged the new fee as unconstitutional, arguing it was a revenue bill that didn't receive the required three-fourths majority vote in the Legislature. The bill passed the House 51-44.

The court rejected a cigarette tax approved earlier this year as unconstitutional for the same reason.