Fund manager Geoff Wilson has voiced “grave concerns” that AGL Energy’s proposed demerger will destroy value for shareholders, providing a firm sign that financially focused investors may join chief opponent Mike Cannon-Brookes in seeking to vote down the split.

Mr Wilson said his firm was “seriously thinking about voting against the demerger”, citing worries about the impact on value from the proposed division of Australia’s biggest electricity generator into coal power-focused Accel Australia and retailer AGL Australia.