The last two of the “big six” gas and electricity suppliers have raised their prices for the second time this year.

The price rises follow announcements in previous weeks from EDF Energy, British Gas, E.ON and Scottish & Southern.

Npower is raising its prices by 26% or £162 for gas and 14% or £60 for electricity, while ScottishPower prices for gas will go up by an average 34% and electricity by 9%.

Both companies said the price rises would take effect from today, with both firms blamed soaring coal and wholesale gas costs for the hikes.

A Scottish Power spokesperson said the wholesale cost of gas had risen 65 per cent since February, while the price of coal had increased by 45 per cent in the same period.

Apologising for the rise, NPower managing director Giuseppe Di Vita said: “We’ve made this decision extremely reluctantly, especially as household budgets are being squeezed so much at the moment.” He added: “There is help available for people who can’t afford to pay their bills and we want our customers to get in touch if they’re worried.”

Willie MacDiarmid, ScottishPower’s director of energy retail, said: “These are difficult times and we understand the financial impact this will have on our customers.”

“The continuing volatility in the global market for gas is directly contributing to increasing UK domestic energy prices and ScottishPower is not immune to these rises. “We have tried hard to keep electricity prices as low as possible and our increase of 9% is the lowest in the sector.”

Tim Wolfenden, head of home services at uSwitch.com, said: “The industry-wide shift to higher household energy prices is now complete. “All the major suppliers have increased prices for a second time this year” “this is a heavy blow and few households will emerge unscathed or unconcerned about the future affordability of their energy.”

Consumers are being advised to check they are paying the lowest possible price for their energy and also to look at reducing their energy usage in the future. Paying by direct debit and moving to an online energy plan, where possible, can help reduce the cost of bills.