Ofgem, which carried out its investigation in partnership with the Financial Conduct Authority (FCA), said that “the interests of consumers had not been harmed”.
The regulator said: “Ofgem and the FCA are taking the unusual step of commenting on the work they have carried out into reviewing these specific allegations because of the concerns those allegations raised among energy consumers.
“Since becoming aware of these allegations, a detailed analysis of all relevant information has been conducted and face to face meetings with a number of market participants were held by both the FCA and Ofgem.”
The FCA added: “Ofgem and the FCA will continue to monitor energy and financial markets, and will work together to consider any evidence of misconduct.”
Industry trade body Energy UK said it was “pleased” with the findings.
“When this problem first arose, our members put out statements confirming they were not involved,” Energy UK said. “The gas market is an international one with many overseas companies trading on it so any allegations of manipulation are very serious and must be fully investigated.
“Customers need to have confidence in markets and authorities need to have the powers to regulate well and take action if required. We are committed to stamping out wrong-doing throughout the market and encourage anyone that has evidence of misconduct to take it to the proper authorities.”
Energy Secretary Ed Davey said: “Regardless of the outcome of these particular allegations I am fully committed to ensuring we have a transparent energy market where the risk of abuse is reduced.
“In view of the importance of the energy markets set out in the Annual Energy Statement I now plan to consult on the introduction of criminal sanctions for energy market manipulation activities.”