Npower and Scottish Power have announced large increases to the cost of electricity and gas, meaning that all six main players in the UK have now done so over the past few weeks.

Scottish Power is increasing gas prices by an average of 34% and electricity by 9% while Npower customers will experience a 26% rise for gas and 14% for electricity.

Both companies blame the soaring cost of wholesale gas and other raw materials while industry body Energywatch urged the government to provide urgent help to those who are struggling to pay energy bills as winter approaches.

"There is strong expectation that the government will shortly announce a raft of measures to protect the most vulnerable," said Energywatch director of campaigns Adam Scorer.

British Gas, E.On, EDF and Scottish and Southern Energy have all raised prices since the end of July.