GAS and electricity supplier npower has apologised to millions of customers after a regular criticised its services.

The German-owned firm, which last week revealed it was sending hundreds of North-East jobs to India, says a computer glitch meant bills and statements were delayed, direct debit payments were not set up properly, and some accounts has problems starting.

Regulator Ofgem said it has been increasingly concerned about npower's customer complaint levels, which came from a serious deterioration in services.

In a letter to npower's 3.4 million domestic customers, Paul Massara, the firm's chief executive, said anyone affected would not lose out financially.

He said the company will also donate £1m to a fund for vulnerable customers, with half of this channelled to Macmillan Cancer Support.

Ofgem today welcomed the apology and payment, and said after its intervention, npower had set out a recovery plan to ensure service levels improve.

Mr Massara said problems arose after customer details were transferred to a new computer system. Its helpline then received extra calls, resulting in longer waiting times for those trying to get through.

He said: “We've let many of you down recently in the overall levels of customer service we've been providing and we apologise unreservedly.”

About 700,000 customers are believed to have been affected by the problems, though it is understood the vast majority are not financially worse off.

Sarah Harrison, Ofgem senior partner, said: “Many npower customers will have noticed a serious deterioration in service levels over the last year.

“The huge growth in complaints is wholly unacceptable and is why we intervened.”

The company is cutting 430 jobs at its Rainton Bridge site in Houghton-le-Spring, Wearside, subject to consultation, and closing branches in Thornaby, near Stockton, and Peterlee, east Durham.

It announced a 10 per cent average bill increase, but said it will reduce bills as a result of a shake-up of Government green levies.