A 10.9 per cent increase in prices for domestic-gas users and a 16 per cent rise for businesses were confirmed by the Commission for Energy Regulation yesterday.
The increases will apply from today, October 1st, and will remain fixed for a minimum period of 12 months.
However, Bord Gáis said that, despite the increase, domestic gas prices in Ireland remain 21 per cent below the EU average and 33 per cent lower in real terms than in 1984. Prices for businesses will be in line with average EU prices, the company said.
Yesterday's announcement follows a 50 per cent increase in crude oil prices in the past 18 months, according to the company.
It also pointed out that residential natural gas prices will be between 17 per cent and 36 per cent cheaper than current prices for competing fuels (oil, electricity and coal).
The Fine Gael spokesman on communications and natural resources, Mr Simon Coveney, said the increase was "despicable" and described it as another example of how consumers were being ripped off.
"It beggars belief that after a summer of approvals for price rises in postage stamps, electricity and phone bills yet another regulator has given the green light to a price rise - this time in gas - well above the rate of inflation," he said.