Best practice guidelines aimed at improving terms for investors in private equity funds globally have failed to make a widespread impact on the industry, dealing a fresh blow to investors in their battle for more power at buyout firms.

Research by data provider Preqin has shown a large proportion of buyout funds have yet to adopt certain principles drawn up by trade body the Institutional Limited Partners Association in September. ILPA's represents global private equity investors and the guidelines were designed to improve the alignment of interests between buyout funds and their backers.