The Association of Convenience Stores has written to the energy regulator Ofgem, calling for all energy suppliers to limit backbills to 12 months.

In December, Ofgem published the results of an investigation into backbilling cases between 2012 and 2013, revealing that over the course of 12 months there had been more than 116,000 cases of backbills reported by suppliers.

While Ofgem noted that the majority of the bills were small, a small minority were worth more than £20,000 and/or lasted more than five years.

ACS chief executive James Lowman said: “For a retailer, an unexpected backbill worth thousands of pounds can be a threat to their business. Many energy suppliers have taken positive steps to reduce the impact of backbills by limiting them to 12 months, as is the case in the domestic sector.

“However, a number of energy companies still refuse to change their policies and this is simply unacceptable. We will continue to campaign for a one-year backbilling limit introduced by all suppliers, and will not accept any more excuses from suppliers.”

In an open letter from October 2012, Ofgem stated that “our analysis of the information from our request does not suggest that any particular supplier or set of suppliers is disproportionately impacted by moving to a limit of one year.”

ACS has been campaigning for a one-year limit on backbilling for several years and has worked with Ofgem, the All Party Parliamentary Small Shops Group and 10 Downing Street to stop excessive backbills being issued to small businesses.

The companies that have committed to a one-year limit are: E.ON, SSE, British Gas, EDF Energy, Npower, Scottish Power, First Utility, Good Energy, and Opus.