Scott Morrison and Bill Shorten have directly questioned each other about superannuation and cancer treatment during the third and final debate of the federal election campaign.

The prime minister and opposition leader are fronting the National Press Club in Canberra in a televised debate moderated by the ABC’s Sabra Lane.

In an attempt to shake up the debate format, the leaders were each given the chance to ask each other two questions.

Mr Morrison used his opportunity to ask the Labor leader how much revenue would be raised by Labor’s changes to superannuation contributions from self-employed workers. 

Mr Shorten failed to answer the question, saying only that the party would release its full policy costings on Friday. 

The Opposition Leader used his question to switch the focus to one of Labor’s signature policies to eliminate out-of-pocket cancer treatment expenses.  

The debate follows what’s been hailed as a defining moment of the election campaign when Mr Shorten delivered an emotional response to an article targeting his late mother.

The Labor leader fought back tears as he talked about his mother and the career challenges she faced, while savaging the “lazy” journalism from the Daily Telegraph.

The rare display of emotion from the Labor leader dominated the campaign on Wednesday, but Mr Morrison will be hoping to wrest back the agenda during the debate.

Mr Morrison will be hoping it’s a case of third time lucky after small studio audiences judged Mr Shorten the winner of the first two debates.  

The debate opened with both leaders naming boat turnbacks as an example of something they have done that was unpopular, but the right thing to do. 

Mr Morrison went back to his first ministry under Tony Abbott, immigration.

“Many of the policies we took to that election to secure our borders, to turn boats back where it was safe to do so were opposed by many people and the turnback policy wasn’t popular,” he said.

“But we did it and achieved the outcome.”

Mr Shorten also nominated his push to have Labor accept the turnback policy in the face of considerable opposition within the party.

“I felt that the experience of defeating the people smugglers proved that Labor needed to change because I have a view that Labor isn’t always right on everything and Liberals aren’t always wrong and of course vice versa,” he said.

The Labor leader drew the first laughter of the night, with a snappy response to a question about his role in the instability that has plagued Australian politics over the past decade.

“I think we need one more change of prime minister then we can finish it for a while,” he said.