Labor will introduce a new Australian environment act and create a commonwealth environmental protection agency, Bill Shorten has announced.

Shorten made the commitment in his opening address to the 48th Labor national conference in Adelaide on Sunday, kicking the event off with two key concessions to the Labor Environment Action Network (Lean).

The announcement defused tension as a deal was reached before a possible conference-floor fight but Shorten’s speech was still overshadowed in part by protesters urging Labor to stop the Adani Carmichael coalmine.

Lean had called for two new agencies – a science-based EPA to oversee development decisions and a national environment commission to develop legally binding plans and standards for protection.

The grassroots environmental lobby group was locked in an arm-wrestle with the shadow environment minister, Tony Burke, who forced the policies out of the draft platform after they were included by administrative error.

In his conference opener, Shorten recommitted to cut carbon emissions by 45% in 2030 and deliver 50% renewable energy by 2030.

“And today I announce that a Labor government will pass a new environment act and create a new commonwealth environmental protection authority to preserve our oceans, rivers, coasts and bushland and to protect the native species that call Australia home,” he said.

Amendments to the Labor platform state the new law will be introduced in its first term of government. The EPA will conduct inquiries, provide advice to the minister, and enforce environmental laws, the platform states.

But rather than create a national environment commission, Labor will instead direct the environment department to establish national environmental plans that will set non-binding “targets and approaches to proactively protect the environment”.

The Lean national convenor Felicity Wade welcomed the announcement, describing it as “a clear marker that Bill is committed to doing the reform that needs to be done”.

“There’s a lot of talk at this conference about unwinding the neoliberal John Howard [era] consensus, and Howard’s environmental laws are one of the manifestations of that that allow the market and business to have free reign over the environment and community,” she told Guardian Australia.

Lean New South Wales executive member David Tierney told the conference the federal environment laws were “not fit for purpose” because they did not mention climate change nor do enough to protect native animals.

“We’re on the path to creating 21st century laws and institutions, although there is more fine detail work to be done,” he said. “Bill Shorten and Labor go to the next federal election with most comprehensive environmental package in many a long year.”

Burke told the conference the new environmental law would “improve the reach of what a Labor government is able to do” and “avoid the ignorance, laziness and determination not to care” about the environment displayed by the Coalition.

A properly-designed EPA will “will give us fair environment laws that make sure we are no longer the extinction capital of the world and make sure when projects need an answer they get one”, he said.

Burke listed recent examples of the current EPBC Act failing or “the government seeming to ignore the law”.

They included large-scale land clearing in Great Barrier Reef catchments, failure to use the water trigger in the assessment of dams and pipelines associated with mining projects, and revelations by Guardian Australia that more than 200 rare and endangered birds had been exported to a German organisation headed by a convicted kidnapper, fraudster and extortionist.

Conservation groups broadly welcomed the platform announced on Sunday, although key details are still to worked through. Under the model, the minister would retain approval powers in decisions relating to matters of national environmental significance.

The national director of the Wilderness Society, Lyndon Schneiders, said the new framework needed “clear goals and the financial resources required to address Australia’s escalating environmental woes, including the extinction and deforestation crises”.

“Labor’s failure to establish a national environment commission is a setback to the development of clear environmental targets and goals against which the effectiveness of the promised new laws can be judged,” he said.

The Greens welcomed the Labor proposals, but its environment spokeswoman Sarah Hanson-Young said “without proper investment and committing to no new coal, oil and gas they will fail”.

As Labor debated the environment chapter inside the conference, protesters outside announced they would organise a second climate strike on 15 March in Adelaide, following high profile student protest actions in November.

Earlier, climate change activists stormed the stage before Shorten’s speech to protest Adani, which recently announced it would self-finance a scaled-down version of the controversial Carmichael mine.

Some had to be dragged away by security, while Shorten accepted a “stop Adani” flag from one protester. In February Shorten had suggested that if elected Labor could revoke approvals for the mine but then ruled out that option.

A second group of protesters raising treatment of refugees in offshore detention also stormed the stage, delaying Shorten’s speech. Shorten then told the conference “the only people [the group] is helping is the current government”.