Australia’s self-declared ‘agile and innovative’ prime minister has hand-picked a new word for 2018 – delivery.

Malcolm Turnbull was keen to talk up his government’s achievements on jobs and economic growth when he phoned into Melbourne radio station 3AW on Friday morning.

With so much going well, what on earth was going wrong, veteran broadcaster Neil Mitchell asked.

Support for the Turnbull government is lower than a year ago across all opinion polls.

‘Well, Neil, you’re the master salesman, so you tell me,’ the prime minister shot back.

‘You are one of the most persuasive salesmen in Australia … so you tell me, how can we sell it better?’

The prime minister, who has turned a Saturday by-election in Bennelong into a referendum on Bill Shorten, accepted it was also a test of his own leadership.

‘In any by-election there is a contest between the two candidates and there is also a contest between the two parties they represent,’ he said.

‘People will be casting a judgment on the government which I lead, of course.’

Mr Turnbull accepted a by-election loss would bring his opposite number closer to pinching his job, and would rob the government of its absolute majority.

‘Confidence in my leadership is a matter for the Liberal party room, and ultimately, of course, on the floor of the house,’ he said.

‘This is why there’s so much at stake.’

Mr Turnbull said time will tell if his government’s popularity improved before the next national poll.

‘The election will be held in the middle of 2019 and that is when people will cast their judgment,’ he said.

‘In the meantime, my job is to deliver economic growth, and we have delivered the longest run of monthly jobs growth since 1994.’

The prime minister brushed off suggestions he was arrogant, after his Monday night appearance on the ABC’s panel program Q&A was widely panned.

‘I enjoyed my appearance on Q&A, I thought it was very well received,’ he said.

‘The worst thing I can do is start to become, as you’re inviting me to be, obsessed with myself. I’m focused on my job, which is looking after other people, and delivering economic growth and jobs.’

The prime minister picked ‘innovation’ as his word for 2017.

‘The (word for) next year is ‘delivery’, and it is putting more money into the pockets of hardworking Australian families and businesses,’ he said.