Treasurer Joe Hockey and Finance Minister Matthias Cormann are changing the rules for the Clean Energy Finance Corporation (CEFC).

The ministers have ordered the green power finance group to make three times its previous targeted returns, while not lifting its risk profile.

The demand comes after earlier attempts to abolish the $10 billion CEFC fund failed.

Insiders say the Federal Government is now trying to hinder its work by setting impossible standards.

Green energy news outlet RenewEconomy has published details of the latest dealings between Hockey, Cormann and the CEFC.

The reports include a letter sent by CEFC chair Jillian Broadbent, in which she describes the near-impossibility of the new target.

Ms Broadbent said the Government was trying to force the CEFC to outperform the market “by a considerable margin”, which would require it to look for investments that were “inconsistent with traditional market-based principles to deliver out-of-market investment returns”.