"And people often doubt that I can. They did that prior to 2013 and they actually ridiculed my plan to stop the boats and they said it wouldnt work and they said it would be dangerous, and they were proved to be wrong."
Mr Morrison had branded Mr Shorten a liar over his declaration that he had "no plans" to increase taxes on superannuation when the Labor Party, in fact, has a suite of policies that would increase revenue from super by at least $30 billion.
On Wednesday, Mr Shorten said he had misunderstood a journalists question, leading him to mistakenly say he had "no plans" to increase taxes on super. "I should have picked the words better, no question," he said.
But Mr Morrison maintained Mr Shorten's original statement was "a lie". Asked if he had ever told a lie himself, Mr Morrison said: "Not intentionally, no."
The Prime Minister insisted he did not break faith with voters when he failed to pass laws protecting LGBTI students from discrimination at school last year - as he had promised - arguing his attempt was thwarted by Mr Shorten's refusal to allow a conscience vote.
"We were trying to do that," he said. "We have our response to the Ruddock report and we'll follow that through."
The Coalition is keen to make trust a central matter of this election, armed with research that suggests voters have not warmed to Mr Shorten and do not regard him as trustworthy.
Mr Morrison hammered home that message on Wednesday as he toured marginal electorates in Tasmania, where the Coalition holds out hope of a surprise win, including in the Launceston seat of Bass.
But the government faces a difficult task to hold on to many of its own seats in Queensland, Victoria and some in NSW - including that of former prime minister Tony Abbott in Warringah.
A day after Mr Abbott rekindled leadership ambitions by saying he was willing to be drafted back into the job of Liberal leader, Mr Morrison left the door open to Mr Abbott returning to the frontbench.
"I have to win an election before I can presume upon making any decisions about those sorts of things," he said. "In order to do that, I need all of my members returned."
Asked to guarantee he would remain as the member for Cook even if he loses the election, Mr Morrison said: "I dont intend to lose this election."