Thousands of ScottishPower energy customers trying to dispute bills have been left on hold for hours due to problems related to the firm’s new £200m IT system, it is claimed.

Twitter is awash with people complaining that the energy giant is trying to "rip us off" as they face waits of up to 90 minutes to get through to the call centre, as well as claiming the website was down for upwards of five hours yesterday.

Alan Bishop, trying to access his account online yesterday, complained: "Your website is STILL unavailable. The message says it’s unavailable until 4pm today. It’s now after 9pm."

Tara Morgan wrote: "Please can someone @ScottishPower call me back! Desperately trying to pay a bill and have been hold most of the wkend!!!!!"

The firm told CBR it has recently migrated customer data to the new IT system, but completed the transition in recent weeks, denying reports that some customers’ details are stuck on the old system.

But a spokesman added that there are still issues with getting staff up to speed on the new software.

"There were some issues but the vast majority of them [customers] have been transferred," he said. "Staff are still getting used to the new system but we’re seeing improvements and we expect this will get better and better."

ScottishPower did not confirm the identity of the new IT supplier before CBR‘s deadline.