Many UK utilities customers face steeply higher energy bills in the coming months as their special tariffs are expiring and they move back on to the full rate for their power.

Around 80,000 Npower customers will be paying £177 a year more for their gas, as their ‘Gas Guardian’ tariff expires this week, meaning the end of a cheap gas price for them.

This tariff was brought in at a fixed price in October 2005 and the expiry date had always been set for January 2007. But those who took advantage of the offer now face bills 39% higher than they have been paying for the past 15 months as they were protected from last year’s increases with cheaper gas price bills.

“The sudden jump in payments will only affect a small minority of our 6.8 million customers,” said a spokesperson.

In addition, British Gas will raise its ‘Click Energy’ discounted tariff for 29,000 online customers this Monday. They will be paying 12.4% more for their gas and 9.4% for their electricity – again forcing many to look for cheaper utility bills.

British Gas customers who have been on its ‘Click Energy’ tariff will now be charged, on average, £336 instead of £303 for electricity, while its gas customers will see the gas price increase and bills rise from £578 to £627.