As Massachusetts hits a climate crossroads, the state’s top law enforcement official is warning that the gas companies are not on track to meet ambitious climate commitments — and urged regulators to impose penalties if the companies don’t step up their efforts to transition away from planet-warming fossil fuels.

Attorney General Andrea Campbell and her team, along with leading environmental advocacy groups and the Healey administration’s Department of Energy Resources in separate briefs, admonished the utilities in new filings before the Department of Public Utilities, telling the regulators that the state’s five gas companies turned in “completely inadequate” climate compliance plans last year.

The gas companies, the AG contends, continue to assert “business-as-usual” plans that are “sidestepping” the DPU’s push for the companies to lay out the costs of the clean energy transition without saddling ratepayers with bloated bills and how they will meet emissions reduction mandates by weaning customers off natural gas.

If the gas companies don’t submit substantially reworked climate compliance plans, the DPU should get tough and impose fines — something that “sends a strong message” and “is a reasonable Department action,” according to the AG.

The latest front in the battle with the state’s utilities — chiefly over the use of natural gas and the supply and distribution network — is a crucial pivot point in whether Massachusetts will be able to cut greenhouse gas emissions by 85 percent compared with 1990 levels by 2050. The building sector represents about 36 percent of greenhouse gas emissions in the state, mostly from old homes and buildings that rely on natural gas as the primary source for heating and cooking.

The state’s ability to slash its emissions at the scale required will depend, in large part, on whether it’s able to electrify those buildings or leverage geothermal energy for heating and cooling while decommissioning gas pipes. Massachusetts will have to manage the cost of that transition while Bay State customers already pay some of the nation’s highest energy bills.

Achieving that feat rests on a central tension: Getting Eversource, National Grid, Unitil, Berkshire Gas, and Liberty to move away from how they currently make money — providing gas to customers.