Two agencies brokering wind sales on Spain's wholesale electricity market, including one owned by wind power company Gamesa, are under an antitrust investigation by the national energy regulator, Comisión Nacional de Energía (CNE), following a complaint lodged against them by Asociación de Comercializadores Independientes de Electricidad (ACIE), an association of independent electricity traders. The two under investigation are Wind to Market (W2M), set up by Gamesa in 2004, and Detisa, owned by the Cepsa oil and gas group. Each currently trades production from over 1000 MW of wind plant, W2M from non-Gamesa operators and Detisa from Acciona plant. ACIE argues that both brokers have contravened regulations set by March 2004's Royal Decree 436 (RD 436), which established incentives for renewable energy generators to trade on the wholesale electricity market. Under RD 436, Spain's top five power groups are not allowed to act as brokers to third parties. ACIE says the fact that both W2M and Detisa's parent companies have shareholders who are in that top five list inevitably means they break RD 436's rules on brokering. In W2M's case, Gamesa is owned 6% by major utility Iberdrola, which also owns 50% of technology investment group, Corporación IBV, which owns 31.78% of Gamesa. Meanwhile, Unión Fenosa has a 5% stake in Detisa's parent, Cepsa. All parties are refusing to comment on the CNE investigation, but prior to W2M's launch, Gamesa's Fernando Ferrando noted that as Iberdrola does not hold an executive position on Gamesa's board, there should be no conflict with RD 436.