Household gas bills are set to soar by more than 20% in the autumn.
Bord Gais asked the energy regulator if it could hike its prices by 28% because of the steep rise in buying fuel from international wholesale suppliers.
But the regulator said it would not allow any more than a 22% jump. The increase is expected to add around 150 euro to the average home gas bill.
The Commission for Energy Regulation (CER) is to officially approve the increase next month. It will come into force at the beginning of October.
Earlier this month, Bord Gais announced that its electricity bills will jump by 12% from August 1. Average electricity prices with Bord Gais currently stand at 989 euro a year, with gas at 689 euro.
The company is already working with 110,000 customers who are behind with their payments.
The National Consumer Agency (NCA) called on the CER to consult with all stakeholders on where the burden of the price hikes should fall. It also demanded the regulator look at solutions for how to spread the load for consumers if the increases of 22% go ahead following the consultation process.
Ann Fitzgerald, NCA chief executive, said the price rises proposed would have a significant effect on consumers' monthly bills.
"We need to ask whether the consumer should have to bear the entire burden or whether it can be spread," she said.
"Consumers should also not take price increases lying down. There is now competition in the gas market for domestic customers, so consumers should consider switching if they find better value with another provider. Switching is easy, takes only minutes and, whilst there is no cost involved, savings can be considerable."