Bill Shorten has signalled Labor will keep the national energy guarantee and maintain subsidies for households and businesses to install small-scale renewable energy until 2030, as the shadow cabinet prepares to deliberate on energy policy.

In a wide-ranging interview marking five years as opposition leader, Shorten also revealed Labor was in talks with the Australian Medical Association about conditions on Nauru, and indicated announcements were coming imminently on what he termed “progressive trade policy”. Some leftwing unions are in open revolt about the party’s decision to support the Trans-Pacific Partnership trade pact.

Shorten all but confirmed Labor would keep the Neg, telling Guardian Australia “we would like to keep that and make it work”. The Coalition has abandoned the energy policy for the electricity sector it championed for months, rendering the prospect of bipartisan agreement highly unlikely, but Shorten said if Labor was blocked in trying to revive the Neg, “we’ll look at other solutions”.

Do they accept that climate change needs to be dealt with or not? Bill Shorten

He blasted the Morrison government for downplaying the conclusions of leading climate scientists, who warned this week there were only a dozen years for global warming to be kept to a maximum of 1.5C.

Shorten declared the Liberals were facing “an existential decision … do they accept that climate change needs to be dealt with or not?

“The idea that they are walking away from that is madness.”

Bill Shorten says there's a 'role for coal' and Adani mine just 'another project' Read more

He said Labor would take a robust climate and energy policy to the next federal election that would incentivise investment in renewables, including maintaining the small-scale renewable energy scheme to 2030.

“We’ve got to end the climate change war. Unfortunately it’s not going to end with bipartisanship – it will come if and when we are elected”.

Play Video 3:48 Australia's climate wars: a decade of dithering – video

Deteriorating conditions on Nauru

Shorten confirmed Labor was consulting the medical community about Nauru, after the Australian Medical Association branded conditions in offshore immigration detention a “humanitarian emergency requiring urgent intervention”. Médecins Sans Frontières this week called for the immediate evacuation of all asylum seekers and refugees.

Labor’s left faction is restive about the condition of children on Nauru after a spate of medical transfers to Australia, and concerns were raised at a meeting of factional convenors and union bosses a week ago as a precursor to debate at the party’s national conference.

There are about 100 children on Nauru, many of whom are in long-term detention. Doctors have appealed for a large cohort to be removed because of a marked deterioration in their physical and mental health.

Treating health professionals should have the principal word in what happens with the treatment of kids Bill Shorten

Shorten said discussions with medical groups had not yet reached a landing point, but “I take what the AMA says very seriously”.

“We think the medical advice should be dominant in decisions made,” he said. “If a child needs medical attention and they can’t get it on Nauru, they should get it in Australia or a third party country. We’re in discussions with the AMA about the best way.”

Shorten said the opinions of medical experts needed to be respected. “I take very seriously the requirement that treating health professionals should have the principal word in what happens with the treatment of kids.”

He said Labor remained resolved to stop new boat arrivals, but that should not mean keeping asylum seekers in indefinite detention.

Trade tensions

The Labor leader acknowledged some trade unions were angry about the parliamentary party’s recent decision to support the Trans-Pacific Partnership , but he said there was no prospect he would reverse that stance.

In confirming support for the TPP-11 enabling legislation last month, Labor promised to introduce laws to prohibit governments from signing trade agreements that waived labour market testing or to include investor-state dispute settlement provisions, which allow foreign companies to sue the Australian government for policy changes.

It won’t be everything unions want, but there will be improvements to the system Bill Shorten

Shorten said more announcements were imminent. The policies are clearly designed to head off a noisy dispute at the ALP conference later this year.

“I’ve explained to the unions there are some benefits in this agreement, not the least of which to farmers, who are doing it tough in drought, and for steel and manufacturing and education,” Shorten said.

“It’s about how you fix the problems and I don’t want to see farmers miss out on the benefits of being an early mover on tariff reductions.

“We are committed to the vote, but what we are going to do is sharpen up a progressive trade agenda.

“We’ve had constructive dialogue with people. It won’t be everything unions want, but there will be improvements to the system.”

Two-tier labour market

Shorten has given some comfort to the Australian Council of Trade Union’s campaign to strengthen industrial relations legislation, saying he is considering calls to restore industry-wide bargaining, a move that would be resisted by many employer groups.

The IR system is tilted against people getting reasonable and moderate pay rises Bill Shorten

“The problem that needs to be solved in Australia is everything is going up apart from people’s wages,” Shorten said. “We think the IR [industrial relations] system is tilted against people getting reasonable and moderate pay rises.”

The Labor leader said a two-tier labour market was developing in Australia, and insecure employment was dampening wage outcomes. He said he was “interested” in exploring ways to improve conditions for workers engaged in long-term casual employment.

“We’ll continue to talk to the unions and other stakeholders, but there is no doubt in my mind if you want to lift productivity, we need to see a fair return for people and the contribution they are making,” Shorten said.

“We haven’t resolved whether industry bargaining is the right mechanism to do that. I’m not against it, I haven’t definitively come out in favour of it.”

Shorten said he wasn’t in the business of shutting down discussion on industry-wide bargaining, but he also suggested a range of measures were required to address the problem of stagnant wages growth.

“I think there’s a range of solutions, I don’t think it’s one size fits all.”

‘The most ambitious policy program since Whitlam’

Federal parliament resumes next week, and a byelection contest in Wentworth looms that could cost the Morrison government its one-seat majority in the lower house.

Shorten said Labor would struggle to take Malcolm Turnbull’s seat from the Liberals next Saturday, even with a strong protest vote. He said the Liberals were likely to hold Wentworth, and on current indications the federal election would be held next year rather than before Christmas.

I feel an obligation to win, but win for purpose. The purpose ... is to restore people’s faith Bill Shorten

He said Labor was competitive in the national contest, but not complacent.

“Some people come up to me and say you should go on holiday and watch the Liberals implode, but I think the pressure is greater because there is great disenchantment with the system as a whole, and I think that puts the pressure on Labor to demonstrate that politics can work for people.

He said voter disillusionment was palpable. “Most people want someone in their corner to respect the contribution they are making rather than [government] by the loudest shouters.

“I feel an obligation to win, but win for purpose. The purpose in part is to restore people’s faith in the system itself.”

Shorten said Labor was ready for battle in the national contest with the “most ambitious policy program since Whitlam”.

Coalition's night terrors play out in public as kill Bill missive backfires | Katharine Murphy Read more

“The best asset that I have got is my intelligent and idealistic team. Tanya [Plibersek] and Penny [Wong] have been invaluable, and Chris Bowen. We’ve got a good gender balance, a lot of the frontbench are working parents and they are in touch. We’ve had our moments, but I really enjoy it.

“I’m doing the things I came into politics to do, I’m trying to improve things that need improving, and we’ve had a few wins, but the main game is to win the election, and hand on a better deal to the next generation.”

Shorten acknowledged that his personal approval ratings in opinion polls were not rosy, but he said his own experience out on the hustings was positive, and Labor had performed strongly in all the major electoral contests during this term.

“I look at where I’ve come from. Wherever I travel in Australia, I feel my recognition rate is increasing. I feel the warmth with which people greet me is increasing. More people want to come up and have a chat and that’s mostly friendly,” Shorten said.

“I’m not short-term poll obsessed.

“I think, in 2018, poll-driven politicians are looking for trouble. You can’t be guided by the polls when people want long term solutions.”