PHOENIX (AP) — A ballot initiative to mandate the use of more clean energy in Arizona is facing a lawsuit seeking to knock it off the ballot over allegedly fraudulent signatures.

Clean Energy for a Healthy Arizona filed more than 480,000 signatures to qualify for the November ballot. But the lawsuit filed Thursday claims that the majority of these signatures are invalid.

The lawsuit says more than 195,000 signatures belong to people who can't vote in Arizona, among other alleged issues.

The signatures were reviewed by an opposition campaign funded by Arizona Public Service Co.

Clean Energy spokesman Rodd McLeod called the lawsuit "delusional," and said APS is spending millions for its opposition campaign.

The Clean Energy proposal would require half the state's energy to come from renewable sources by 2020.