The new tariffs will represent an increase of almost one third on existing rates.
This time last year Phoenix Natural Gas, the main supplier in Northern Ireland, reduced its prices by almost 15%.
However, following a huge increase in global energy costs for oil and gas, Phoenix is now increasing its charges by 28%.
From 1 May, over 100,000 householders in the greater Belfast area will see their bills rise by £2.50 a week, or £130 a year.
The average gas bill will now be around £590 per annum.
Phoenix says it understands the huge increase will be unwelcome news, but maintains that gas remains 20% cheaper than home heating oil.
It also promises that if worldwide prices for wholesale gas fall in the future, its prices to homes will drop accordingly.
