The Department explained that no single organisation has overall responsibility for preventing and detecting fraud on ECO4 and GBIS.79 Ofgem’s role in relation to fraud is limited to progressing counter-fraud investigations where allegations have been made.80 Ofgem explained to us that it has neither a legislative role nor the ability to detect fraud across the whole system. It told us it had identified installations worth 1.75% of the scheme value as fraudulent as of November 2025, which is below the 2% departmental threshold for fraud.81 However, this is detected rather than estimated fraud. The National Audit Office reported that Ofgem had estimated businesses could have fraudulently claimed between £56 million and £165 million from energy suppliers under ECO, which would be up to 3.9% of the £4.2 billion scheme delivery costs to the end of March 2025. It also reported that there were separate suspicions of other fraudulent activity that was not included in this estimate.82