OTTAWA -- The federal government is increasing the carbon tax on new natural-gas plants to discourage power companies from building them.

The change is part of final regulations for the government's carbon-tax system for big industrial greenhouse-gas emitters, which are being released this week.

The system affects businesses that produce more than 50,000 tonnes of greenhouse gases a year.

It is designed to limit impacts on competitiveness for major industrial emitters, who will pay the carbon tax on a portion of what they emit rather than on all the fuels that they use.

The emission standard set for natural-gas power plants originally meant that new ones would likely never pay any carbon tax, which was a disincentive for power companies to turn to renewable-energy sources instead of gas.

The change made this week means new natural-gas plants will have their emissions standard toughened each year after 2021, until in 2030 they will pay the carbon price on every ounce of their emissions.