SACRAMENTO — The fight over California’s landmark internet-privacy law could soon lead to warfare between tech companies and privacy-rights advocates at the ballot box.

Alastair Mactaggart, a wealthy San Francisco developer, said he plans to bankroll an initiative asking voters to expand the California Consumer Privacy Act. The measure would enshrine the act in state law so legislators could not weaken it, he said.

His proposal would also create a state agency to enforce consumer privacy protections and triple penalties for companies that break laws regarding the collection and sale of children’s private information.

“The only thing I want to make sure is they can’t undo the act,” Mactaggart told The Chronicle. “There is basically unlimited resources on one side of the fight. If you don’t do anything, they will win eventually.”