The trade union said the RIIO proposals, which allowed less investment than the gas distribution networks (GDNs) sought, would make the industry less safe.
Scotia Gas Networks publicly accepted the proposals in January and the other GDNs are understood to have followed suit.
National secretary for energy and utilities Gary Smith said: “This 20% cut in investment by Ofgem will cause more gas leaks. Ofgem’s RIIO formula takes no account whatsoever of the dangers in handling the volatile and highly explosive substance… Gas main replacement will be cut and gas workers aren’t going to be able to cope with gas escapes if it gets cold. An increased risk of loss of life as a direct result is inevitable.”
Ofgem said it was for the GDNs to appeal to the Competition Commission if the price control did not allow them to meet their safety obligations.
A spokesperson said: “Under the RIIO price controls the GDNs are required to provide consumers with safe and reliable network services at a fair price. The network companies have clear safety obligations which are set out and enforced by the Health and Safety Executive. If any network company considered that the terms of our price control do not enable them to meet their safety obligations, they have the responsibility to set this out and appeal to the Competition Commission.”