German utility E.ON has submitted a letter to the Spanish stock market regulators accusing Acciona of engaging in collusion to block its proposed takeover of Iberian power firm Endesa.

According to the Dow Jones Marketwatch, E.ON suggests in its letter that Spanish businessman Manuel Jove has acquired 4% of Endesa’s shares and that the move was backed by Acciona as part of a strategy by the construction and renewable energy firm to build up a bank of shareholders capable of blocking E.ON’s move for its power contemporary.

Apparently, E.ON also alleges that its chief takeover rival, Gas Natural, is acting in collusion with Acciona. Furthermore, E.ON alleges that Acciona is looking to secure the support of other Endesa shareholders, including Caja Madrid bank and Energias de Portugal. The German firm wants the Spanish regulator to probe the recent share dealings in Endesa.

The revelations come as other news reports suggest that Acciona itself has increased its stake in Endesa by 1% to 21%.