PG&E Corp. falsified natural gas pipeline-safety records over five years, California regulators said Friday, dealing another blow to the state’s largest utility as it struggles with mounting lawsuits stemming from devastating wildfires.

The California Public Utilities Commission said an investigation by its safety division found that PG&E lacked sufficient staffing to locate and mark natural-gas pipelines as required by law, and pressured employees to complete the work.

As...