SCOTTISHPOWER apologised for keeping customers hanging on yesterday – hours before it took our reporters 46 minutes to get through on their hotline.The energy giant, who have 5.8million customers, said sorry for keeping long-suffering callers waiting to speak to an agent for up to an hour.But when the Sunday Mail called yesterday to test the customer service line, one call took 46 minutes and 12 seconds to reach an agent, despite promised improvements.After a warning that high call volumes may mean a longer waiting time than normal, we were subjected to a stream of messages and music on a constant loop, including Huey Lewis’s The Power Of Love and Paolo Nutini’s New Shoes.Another call we placed was answered just after eight minutes, while a third call took 10 minutes to answer. Two additional calls were answered by an operator within two minutes.Tom Greatrex, Labour’s shadow energy minister, said: “This is simply unacceptable. They need to sort themselves out and quickly. Customers deserve better.”The energy giant’s profits fell 11 per cent to £263million last year and problems with customer service emerged a few months ago, with scores of calls, emails and website contacts reportedly going unanswered.A spokeswoman for Consumer magazine Which? said: “It’s disappointing that ScottishPower customers are being left waiting on hold for far too long. Our research found it seems to be getting worse with other energy companies too.