SA Opposition Leader Steven Marshall has used an environmental debate to attack SA-BEST Leader Nick Xenophon for a lack of policies, while trading barbs with Labor over renewables.

The debate was hosted on Tuesday by leading environmental groups including Conservation SA and the Wilderness Society, giving the leaders the chance to sell their green credentials heading into the March state election.

Mr Marshall said Mr Xenophen had failed the environment.

"On nearly every single topic he's got a buffer or a stopper or something to talk about, which really gets away from the fact that SA-BEST has no policies whatsoever to enhance the environment," he said.

Premier Jay Weatherill and Greens leader Mark Parnell were also at the debate, which covered nuclear waste, marine sanctuaries, drilling in the Great Australian Bight and fracking.

The premier and opposition leader clashed over renewables, with Mr Weatherill calling the March 17 election a "referendum on renewable energy".

He condemned Mr Marshall's vow to scrap the state's renewable energy target if elected.

"If you choose the Liberal party or Nick Xenophon at the next election what you will have is sending a message to the nation and to the world that we're turning our back on renewable energy," he said.

The premier also accused Mr Marshall of "scare-mongering" and said he had never apologised for a television appearance on the night of the blackout, during which he said the generators do not work when the wind blows too hard, and that the Royal Adelaide Hospital had been blacked out.

Instead of a state target, the Liberals would support the National Energy Guarantee, which comprises both a reliability and an emissions target.

Mr Marshall said a national approach would deliver the best outcome, while Mr Xenophon was more critical of the policy.

"We haven't ruled it out, but in its current form I think it has a number of very deep flaws," he said.

Mr Parnell said the Greens strongly support renewable energy targets at both the national and state level.