Calls for inquiry after fourth power price rise

The government was coming under renewed pressure last night to launch an investigation into the home energy market after Scottish Power became the fourth power firm to announce an almost identical price increase to its rivals.

Scottish Power said yesterday it would raise gas bills by 15%, while electricity bills will go up by an average of 14%.

The price increases, which come into force today, will see Scottish Power's average dual fuel bill rise by £123 a year to £959. The Spanish-owned company said the price rises would affect 4 million out of a total of 5.2 million customers who were not on a price-protected tariff.

The move, which was once again blamed on higher wholesale costs, immediately led to renewed calls for a Competition Commission investigation into "tacit collusion" by the UK's big six power firms.

Consumer groups pointed out that the price difference between the four firms that have raised prices is just £13 on a total gas and electricity bill of over £1,000.

Willie MacDiarmid, ScottishPower's director of energy retail, said: "We have worked hard to protect our customers from these increases for as long as possible. Our input costs are now at record levels, having increased by up to 97% since February 2007."

In January Npower increased gas prices by 19%. EDF and British Gas followed with increases of 13% and 15%. All four companies have claimed hugely differing wholesale increases.