The target was hatched in a room above a pub in central ­Melbourne in late 2014 by a self-declared “scraggly bunch” of ­environmentalists operating within the party.

A re-energised Labor Environment Action Network went on to mount an aggressive grassroots campaign across the ALP branch network that conquered party heavyweights despite strong objections from the CFMEU.

Bill Shorten adopted LEAN’s 50 per cent renewables target by 2030 shortly before the ALP’s ­national conference last year, ­admitting he had no idea how the party would get there.

Energy Minister Josh Frydenberg yesterday accused the ­Opposition Leader in parliament of a “reckless pursuit” of an “ideological approach” to the target without thinking through the consequences.

Citing a Bloomberg New ­Energy Finance Report, Mr Frydenberg warned the Labor policy would cost $48 billion and took aim at Mr Shorten for refusing to explain how to achieve the 50 per cent target until October next year. “We are told that will ­require 10,000 turbines. Where are they going to be built?” Mr Frydenberg said. “If you had a $48bn program, you’d expect you’d have a bit of detail to show.”

In response, Labor sought to pressure Malcolm Turnbull over his plans to support renewable energy projects beyond 2020, with opposition energy spokesman Mark Butler saying the government had no policy and was wedded to coal as Australia’s “only energy future”.

LEAN organiser Felicity Wade said yesterday the statewide electricity blackout in South Australia had pushed debate past renewable energy targets to the need for greater market intervention. “Of course there is a huge debate in South Australia,” Ms Wade said.

“Targets are all very well but that is not where the debate is at. We need to reform the national electricity market and start a discussion on whether we can expect the market to do it.”

LEAN was set up in 2004 as a cross-factional environment ­organisation within the ALP by Jenny McAllister, who is now a senator, and former NSW premier Kristina Keneally.

The organisation welcomes ALP members but not members of any other party and has heavyweight patronage including federal environment spokesman Tony Burke in NSW.

Ms Wade, a former Wilderness Society campaigner and partner to Wilderness Society ­national campaign director Lyndon Schneiders, said LEAN had been revived just before the 2013 Labor election loss out of concern about what would happen to climate change policy in light of the disastrous carbon tax experience.

Ms Wade said senior figures in the ALP had warned her that if she cared about climate change she should back off and leave the issue until Labor was back in government.

She said the 50 per cent renewables policy was developed by a “scraggly bunch” who believed Labor needed to make climate change a conviction issue, not a tactical one.

For policy, the group took its lead from an international report by ClimateWorks, which set out a road map for decarbonisation and identified ways to get to net zero emissions by 2050.

“It was a light-bulb moment because here was a piece-by-piece plan,” Ms Wade said.

“That report had 50 per cent renewables by 2030 to net zero by 2050. We stole that target, which at the time was regarded as huge.”

Ms Wade said that while the climate change response was being set up as an environmental agenda it crossed into key Labor concerns of jobs, growth and ­security. She said there had been a “lack of recognition in the party” that “if we retool the energy sector there are major ideological ­issues”.

“When we designed the last energy system it was done by the state and planned,” she said.

“With South Australia we can see how hard it is to redesign the system using market incentives. Labor should be having these discussions. Are we going to import every last bit of plant or are we going to be active in saying we could have a piece of that?

“I am not saying go back to 1950s protectionism but there are huge public policy issues.

“It is in the ALP’s interest to have future-facing policies and natural heritage considerations in deciding the energy transition.”

LEAN started its renewables push with a simple PowerPoint presentation, a voiceover and brochure, and hit the road to ­explain it branch to branch. By the time it got to the ALP national conference, LEAN had 370 branches supporting the target.

“We had a clear mandate from members,” Ms Wade said. “But weeks out from the conference the CFMEU wrote to the ALP leadership saying they did not like the policy. We thought it was ­derailed but we held our ground.’’

The target was accepted as ALP policy and taken to the federal election. It has since been adopted by the Queensland Labor government. Mr Shorten has described the target as an ­ambition. “There’s a long way to go in terms of working through all the issues and details,” Mr Shorten said last year.

In the party’s Climate Change Action Plan during the election campaign, Mr Shorten said Labor would “announce the proposed design details by 1 October 2017 with legislation for post-2020 ­arrangements to be introduced to parliament in late 2017”.

Additional reporting: Joe Kelly