Billionaire having 'red-hot crack' at AGL

"It's an uphill battle. Look, we're having a red-hot crack," the tech mogul told AAP on Tuesday.

Newly installed as AGL Energy's largest shareholder, he said the current board's plan to split the company into something "smaller and weaker" would be a poor outcome for investors, workers, and the climate.

His push to more quickly power Australia with renewable energy comes amid a tight election where climate politics is heartfelt by those hit by more severe and frequent floods, storms and bushfires.

Ultimately the government, and the taxpayer, would have to foot the bill if the AGL board gets its way, he said.

But it's not an idealistic pledge.

Rather, he sees a compelling future for AGL Energy at the helm of Australia's rapid transformation.

"It's an investment. It's not being done by a philanthropic group. It's being done by my investment group," he said.

"I'm not throwing away $650 million."

The AGL Energy board has dismissed his criticism of the imminent split of the company, saying in a statement to the ASX on Tuesday that the demerger is in the best interests of all shareholders.

The Atlassian co-founder tweeted on Monday night he had built his stake in AGL Energy to more than 11 per cent, seeking to influence its future by becoming the largest shareholder and rallying others to his cause.

"It's a really critical moment," Mr Cannon-Brookes said.

"It has a bright future but it's not going to harness that future by demerging."

His intervention comes after AGL issued a letter to shareholders asking them to back the board's plan to split the company into an energy retailer called AGL Australia and a coal-fired electricity generator called Accel Energy.

The new entities will have a target to reduce emissions to net zero by 2040 and 2047, respectively, which is too slow for the biggest shareholder.

AGL said it remains committed to "a responsible transition of Australia's energy system" and plans to split the company by June 30.

For the demerger to succeed, 75 per cent shareholder approval is required when the vote is held on June 15.

Superannuation fund Hesta, which owns a 0.36 per cent stake on behalf of its members, is against the demerger.

"We're not convinced the proposed AGL demerger will achieve emissions reduction and coal asset closure aligned with the Paris Agreement, nor that AGL's plans provide an equitable transition for affected workers or communities," Hesta CEO Debby Blakey told AAP.

Mr Cannon-Brookes said many shareholders - big and small - are worried but have only been presented with one option by the board.

"There's one candidate, there's one box, put a number in a box, but there's only one box," he said.

"The way it's been set up by the company, to say there is no other option, is frustrating a lot of shareholders."

Asked on the campaign trail whether it was embarrassing that a tech billionaire was showing more leadership on emissions, Scott Morrison said his government had a practical plan for net zero by 2050.

"If you allow electricity prices to rise by having unbalanced emissions reduction targets, then the price of all of this goes up," he told reporters.

Mr Cannon-Brookes has launched a website - Keep it together Australia - setting out his case for shareholders to block the demerger.

The timing is driven by the demerger timetable, after the board rejected his takeover bid earlier this year.

"The only thing I'm focused on is winning this vote," he said.

"I know there's another campaign going on, but I've spent far less time thinking about it."

Australian Associated Press