Mr Shorten held a koala and met a five-month old koala joey at Australia Zoo before outlining his $1 billion package for environmental initiatives.

"I just don't want my children to come and see flora and fauna, I want their children to come and see it and future generations to see what makes Australia so special," he told reporters.

"I think most Australians will be surprised to learn that when it comes to the rate of animal extinctions, we're fourth worst in the world. We need to do more."

The zoo sits outside of Brisbane, which is in the electorate of Fisher - a seat the coalition holds by 9.2 per cent.

Mr Shorten also visited a shopping centre in the seat of Petrie, which the coalition holds by 1.7 per cent.

He was joined by the local candidate Corinne Mulholland, Labor's pick for the neighbouring seat of Dickson, Ali France, as well as MPs Susan Lamb and Kristina Keneally.

Mr Shorten heard from a wide spectrum of supporters, with a young boy telling him he would make a great prime minister, a first-time voter grilling him on climate change and a man yelling out "Pauline Hanson for PM".

Labor's environment plan includes $100 million for a native species protection fund and $62 million to tackle coastal erosion by preparing Australia's beaches for climate change.

Mr Shorten also promised $50 million for a national environmental protection authority and for federal environment laws.

Climate remains a hot topic ahead of the May 18 election, with new polling showing West Australian voters aren't worried about the cost of action on climate change, but just want something done.

The Labor leader won the leaders' debate on Friday evening, making it two from two in his policy battles with Prime Minister Scott Morrison.

During the debate, Mr Shorten hinted at plans to make multinationals pay more tax.

But punters are more focused on a moment where the two leaders ended up standing close together, with Mr Shorten telling the prime minister he was a "classic space invader".

Both leaders are being dogged by controversial candidates, with the Liberals losing nine since the election was called, while Labor has lost four.

The latest to fall was the party's candidate for the seat of Melbourne Luke Creasey, who stepped aside on Friday after more offensive social posts were revealed.

"When the very first post that he shared emerged we said it was stupid ... but then it was clear there was not just one post and there were more, and I wasn't prepared to keep defending the situation," he said.

Mr Shorten says he has not seen the anti-asylum seeker posts which his candidate for the Western Australia seat of Durack, Sharyn Morrow, shared on social media in 2013.

Australian Associated Press