Ofgem has launched an investigation into National Grid and ScottishPower over the delivery and ongoing operation of a £1.3 billion subsea cable that transports electricity between Scotland, Wales and England.

The Western HVDC project was undertaken by a joint venture between National Grid Electricity Transmission (NGET) and ScottishPower Transmission (SPT).

The investigation will review the performance of the two organisations in delivering the cable and will consider whether its late delivery means they breached licence conditions.

It was originally due to be completed in late 2015 but electricity did not start flowing through the subsea cable until December 2017, however, it was not fully operational and suffered outages.

Ofgem said: “The opening of this investigation does not imply that we have made any findings about non-compliance by National Grid Electricity Transmission or Scottish Power Transmission.”

NGET and SPT said in a joint statement: “We will continue to work with Ofgem in an open and transparent manner and will fully co-operate with this investigation.

“We are confident that our investment in the link has delivered benefits for consumers since entering service in 2017 and will continue to deliver benefits. We are committed to providing a reliable link that will transport cleaner greener energy to our homes and businesses across Great Britain.

“We are working hard to repair the current cable fault and are certain we will overcome these difficulties and establish a link that will continue to benefit consumers for many years to come.”