ScottishPower today announced it was increasing gas prices by an average 34% and electricity prices by 9%.

The Spanish-owned company, which has 5.2 million customers, blamed soaring coal and wholesale gas costs for the increases, which will take effect from Monday.

It said the average dual fuel customer would see bills increasing by 25%.

The company said the wholesale cost of gas had risen 65% since February, while the price of coal had increased by 45% in the same period.

It said about 1.2 million customers were currently protected by fixed-price tariffs. The company today offered a new tariff guaranteeing prices until December 2009.

These are difficult times and we understand the financial impact this announcement will have on our customers. Willie MacDiarmid

The Glasgow-based firm is the latest to hit households with steep hikes in gas and electricity prices in recent weeks, following moves by British Gas, EDF, E.On and Scottish & Southern Energy.

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

"Although we're one of the last companies to announce increases, we're sorry we couldn't hold on any longer. However, we have worked very hard to protect people for as long as possible from these considerable increases in the wholesale market.

"We have tried hard to keep electricity prices as low as possible and our increase of 9% is the lowest in the sector.

"The continuing volatility in the global market for gas is directly contributing to increasing UK's domestic energy prices and ScottishPower is not immune to these rises."

Spanish energy conglomerate Iberdrola bought ScottishPower last year for £11.6bn