Massive gas companies building projects in Australia could claim the costs of cleaning up environmental disasters as a tax break, a Senate inquiry has heard.

The royalty system for gas under the federal petroleum resource rent tax (PRRT) sees miners pay a tax on profits after accounting for a series of deductions, including building costs.

The system, which is under review by the Turnbull government, has faced heavy criticism as miners have written off massive project costs meaning they pay little or no tax.

The hearing was told that companies could get tax concessions for oil spills through the costs incurred by cleaning up the coastline or getting salvage equipment shipped from overseas.