Phoenix Gas puts prices up by 39% in Belfast and Larne
Phoenix Gas is to increase its prices by 39%, with the company blaming the rise on wholesale fuel costs.
The price increase begins on 1 May and will apply to Phoenix Supply domestic and small business customers in the greater Belfast and Larne areas.
The Utility Regulator chief executive Shane Lynch said he was conscious of the impact on household budgets in NI.
"We scrutinise all price rises to ensure that the maximum tariff Phoenix can charge is justified," he said.
"This increase is wholly attributable to rising wholesale gas costs."
The move is expected to push the average household bill to over £580 a year.
Phoenix's competitor Firmus has said it will be holding consumer prices until the end of September.
The Consumer Council said the price hike was a "massive blow" and risked pushing more consumers into fuel poverty.
Consumer Council chief executive Antoinette McKeown said they were calling on Phoenix to take action to help some of the most vulnerable households.
"They can identify customers that are struggling early on and give them the assistance they need," she said.
"They could create suitable payment plans and find suitable alternatives to disconnection to help those hit the hardest by this rise."
"It is unfortunate that those who are on pay-as-you-go tariffs are unable to switch supplier, it is those customers, who are usually the poorest, that end up paying the most."
"We are, as always, encouraging customers to shop around and get the best deal."
BBC Northern Ireland Consumer Affairs Correspondent Martin Cassidy said it remains unclear whether customers will switch suppliers.
"Logic might suggest an avalanche of people signing up with Firmus but consumer behaviour is sometimes a complex thing," he said.
"Certainly there will be an initial surge but Phoenix seems quite relaxed about it all and point out that in Britain where there are six companies battling it out for market share, not all that many customers actually bother to switch.
"Many customers see changing supplier a hassle even though the process is relatively easy and fast," he added.
"It is going to make for an interesting time to watch what consumers actually do. Younger and more IT-literate consumers are much more likely to respond to the big price difference."
Around the world oil prices have risen by 83% as first China and more recently the United States and many European countries have seen their economies begin to recover.
The biggest rises though, have come in the past two months with the oil market surging 29% in response to the conflicts in north Africa and the Middle East.
And as well as worries over oil supplies, events in Japan have resulted in increased demand for liquefied natural gas.