Prospect Deputy General Secretary Garry Graham said: "Prospect has consistently argued for the need for transparency in relation to how the energy market operates.

"It is important that consumers are confident that they are receiving value for money in relation to their energy bills. But the current debate on energy policy has failed to fully appreciate the pressing need for investment in capacity, infrastructure and the replenishment of skills within the industry."

Graham said OFGEM's own figures illustrating the decline in capacity margins serve only to highlight the need for investment while international events add impetus to the need to address issues of capacity and security of supply.

"Given the current political debate in the UK, the referral to the CMA is perhaps understandable. But there is a real danger that another period of uncertainty will stymie investment and push us closer to the day when the lights go out.

"The UK has the opportunity to be a world leader in future low carbon energy generation and investment and innovation are key to this. Of course, customers' interests should be at the heart of what the energy companies do but simply demonising the 'big six' as some have done does not constitute a coherent energy policy."