U.K. dance music empire Ministry of Sound has issued its second "open letter" to AIM within 48 hours, this time lining-up Warner Music Group in its crosshairs and criticising AIM's acceptance of a Non-Disclosure Agreement covering the deal with the major label.

The London-based firm had earlier resigned from AIM, the U.K. independent music companies' trade body, in protest of Impala's support of WMG's bid for EMI. AIM is a member of Impala, the Brussels-based trade body for European independent music firms. Fellow AIM member Gut subsequently followed MoS' lead, and exited AIM.

As a response to those departures, AIM yesterday hosted an "emergency" board meeting at its London headquarters, during which its key executives drilled into confidential documentation on Impala's agreement with WMG.

MoS Music Group managing director Lohan Presencer attended the early part of the meeting, but baulked at the NDA which was put on the table for all attendees to sign.

"If WMG wish this matter to be resolved without reference to the European Commission, then they must and will agree to the terms of the agreement with Impala being debated openly and transparently," MoS wrote in its latest letter, issued by its legal representatives Blake Lapthorn Tarlo Lyons.

In the letter, MoS adds that it is prepared to attend AIM's upcoming monthly board meeting next Tuesday, at which the terms of agreement will be further analysed. However, it says it will only join on the condition that the restricted document was "disclosed in advance and publicly circulated" and without constraints.

Warner Music Group declined to comment.