Australia's biggest energy company on Friday released the demerger booklet required by regulators for the board's plan to create an energy retailer - AGL Australia - and a coal-fired electricity generator - Accel Energy.

"This demerger is a turd rolled in glitter, but the marketing sparkle is fooling no one," said Glenn Walker, Greenpeace Australia Pacific senior campaigner.

Dan Gocher, a director at the Australasian Centre for Corporate Responsibility, said alignment with the Paris climate agreement across both demerged entities was a fundamental demand of a majority of AGL's shareholders less than a year ago.

"We don't expect AGL's largest shareholders will take well to being ignored," he said.

According to the International Energy Agency and United Nations climate bodies, alignment with the Paris Agreement would mean closing coal-fired power stations in OECD countries by 2030.

Grant Samuel, the independent expert commissioned by the board, has found the demerger is in the best interests of shareholders, according to the document released to the ASX.

Justifying the split, rapid change in the national electricity market towards renewable generation has impacted on AGL's structure as a gentailer - generator and retailer of energy - the company said.

"The demerger is the next step in AGL Energy's history of leading change in the energy company."

A "strong future" for both parts of the business and long-term shareholder value will be created, it said.

The booklet reiterates AGL Australia will target net zero emissions by 2040 and Accel Energy by 2047, which is too slow for the biggest shareholder billionaire Mike Cannon-Brookes.

His investment vehicle Grok Ventures remains staunchly opposed to the split.

A Grok spokesperson told AAP that AGL shareholders only need to see the risks and disadvantages section of the demerger booklet far outweigh any advantages put forward by the company.

"The booklet does nothing to change our view that the demerger plan promotes a terrible outcome for shareholders, communities and the climate," the spokesperson said.

The booklet states that it would be better to split rather than have both arms of the business competing for investors at the same time.

But Accel Energy could be denied access capital and insurance due to environmental, social and governance (ESG) concerns about its coal-fired power plants, according to Greenpeace.

Mr Cannon-Brookes has built up a stake of more than 11 per cent and is campaigning for shareholders to join him and block the split.

He failed in his bid earlier this year to buy out the company, take it private and rapidly replace its coal assets with renewables this decade in line with global momentum.

AGL shares closed down 7 cents at $8.35, above the tech mogul's sweetened March offer of $8.25 a share that the board rebuffed as undervaluing the company.

AGL board plans to implement the split by June 30, after shareholders vote on June 15.

There is a long-term plan for Accel to turn fossil fuel generation assets into lower-emission industrial hubs.

AGL Australia will develop, operate and manage a portfolio of gas, hydro and battery storage assets.

Australian Associated Press