TORONTO -- Ontario's Liberal government is defending the decision not to display the costs of its cap-and-trade program to fight climate change on natural gas bills.

The Ontario Energy Board this week told natural gas companies to separately show their costs of cap-and-trade on tariff sheets posted on their websites, after ruling earlier that those costs would not be listed as a line item on monthly bills.

Energy Minister Glenn Thibeault says the energy board views the costs of the program designed to reduce greenhouse gas emissions like labour or pipes or any other cost of doing business, which are not shown on bills.

Thibeault says he "respects" the decision by the OEB, which he describes as "a quasi-judicial organization that looks after bills in the natural gas sector," while the government is responsible for electricity bills.

The Liberals predict cap-and-trade will add about $5 a month to residential natural gas bills when the program starts January 1, but insist they can't tell the energy board what to display on those bills.

The OEB has also approved rate increases effective Oct. 1 for natural gas distributors that will add between $22 and $40 a year to residential bills.