A ballot measure proposing to tax California's wealthiest residents has collected sufficient signatures to appear before voters, according to supporters of the initiative.

The measure would impose a one-time 5 percent tax on assets of California residents with net worth of at least $1.1 billion. Backers say they have gathered the required number of signatures to qualify the proposal for an upcoming election.

Opponents of the billionaire tax have mobilized significant financial resources to counter the measure. Pacific Gas & Electric has contributed nearly $10 million to an anti-tax political action committee called Californians for Resilient and Affordable Energy, which is working to defeat the proposal.

The utility company's substantial investment reflects broader corporate opposition to the wealth tax initiative. Critics argue the measure could drive wealthy residents out of California and harm the state's economy.

In addition to funding opposition campaigns, opponents are backing competing ballot measures designed to counter the billionaire tax proposal. These alternative measures represent another strategy to defeat or dilute support for the wealth tax.

The ballot qualification sets up what is likely to be an expensive and contentious campaign over California's tax policy and treatment of its wealthiest residents. The outcome could influence similar wealth tax proposals in other states.