The adjudication finds that Your Energy made 'misleading' claims about the supposed CO2 savings for their West Hinkley proposal in Somerset.
The company's original planning application for 12 turbines near the Hinkley Point nuclear power station was rejected by the local authority in 2005.
The company appealed the decision in December 2005, only to withdraw their appeal over a year later after putting in a parallel revised application for nine turbines.
In July this year, the Secretary of State for Local Government ordered Your Energy to repay the local council £10,000 towards the costs it incurred in preparing for the appeal.
Planning appeal costs are usually paid by the relevant parties, regardless of outcome. However, the Secretary of State can award costs on the grounds of unreasonable behaviour which results in unnecessary expense.
A spokesman for Moorsyde Action Group (MAG) said: "News of the ASA ruling comes as no great surprise. The company have used the same misleading calculation of carbon savings here, but they normally take care not to publish this sort of material in anything that the ASA would class as an advertisement.
"MAG has recently been in touch with the ASA about a so-called 'Moorsyde Newsletter' which is available for download on the Your Energy website. The ASA tell us that they can't take action on this because, unlike a print version that is distributed to the public, it is not deemed to be an advertisement."
The spokesman continued: "In July, Your Energy sent a letter with a 'Summary' of the 'Moorsyde' proposal to members of the Berwick Borough Council's Planning Committee. This document is only two sides of A4 but, as in their previous letters to councillors, contains many factual errors and misrepresentations.
"We would like to take this opportunity to publicly challenge Your Energy to publish this 'Summary' as a printed leaflet. This would enable us to make a formal complaint about it to the ASA.
"If Your Energy will not expose this document to public examination, we will display it on our website together with a point-by-point critique of its errors and misrepresentations. We will also ensure that councillors receive a copy of this analysis."
Your Energy say the problem has been caused by a change in the guidelines recommended by the British Wind Energy Association (BWEA). Whereas their original calculations were based on carbon dioxide savings of 860g CO2/kWh, the ASA ruling has determined a preferred figure of 430g CO2/kWh which covers all forms of power generation, including nuclear power.
Alison Hood of Your Energy said: "The output of the wind farm is not in dispute – the nine turbines will supply the equivalent of around 10,200 homes with clean, renewable energy."
The company have agreed to use the new figure in any future publications.
The Moorsyde application, together with other applications at Toft Hill, near Grindon, Barmoor, near Lowick, and Wandylaw, ne