During a sometimes emotional speech to the ACT Assembly after being elected as chief minister in a special sitting on Thursday, he turned to his partner in the public gallery and declared, "Anthony, I love you and I look forward to the day when we can legally marry in this country".

Mr Barr reiterated plans to campaign on same-sex marriage during his chief ministership in a later press conference, where he also stressed the jobs message by holding the press conference wearing a hard hat and fluoro vest at an apartment building construction site in Braddon.

After his election as chief minister in front of a packed public gallery, he told the Assembly that from former chief minister Jon Stanhope he had learned that Canberra "wants and deserves leadership with a progressive vision and voice". From Katy Gallagher, he had learned "above all that leadership is about people; she reminds me of it in her words and in her deeds every single day".

Mr Stanhope had led a fiscally responsible government through many years of growth, and Ms Gallagher had worked to keep the city strong after the financial crisis. But the economy was no longer a backdrop.

"For the Barr Labor Government the economy is centre stage, and as chief minister for the ACT, jobs for Canberra is my leading role."

Mr Barr said Canberra had lost the two certainties it had relied on since self-government - the strong underpinning from the national economy, and support from a friendly federal government. Canberra must now stand by itself, and he would bring his "background and outlook, knowledge and skills as a student of the economy, as a passionate advocate for economic growth, and as treasurer of the ACT" to the task, he said.

Mr Barr reassured owners of Mr Fluffy asbestos-contaminated homes that "you have not lost a chief minister who cares", and pointed out that would gain a senator, in Ms Gallagher, who understood the issues.

And he restated his commitment to the tram line.

"Capital Metro is vital to Canberra's economic future ... and I will be enormously proud to lead the government that will deliver it," he said. "It's the right decision. Our city needs jobs and Capital Metro supports jobs; our city needs investment and Capital Metro supports investment; our city needs a diverse, balanced economy and Capital Metro supports a diverse, balanced economy; our city needs growing returns on land and Capital Metro supports growing returns on land."

Mr Barr, who is confronting a budget deficit of more than $500 million and thousands of job cuts in the federal public service, said Canberra was confronting the most testing external economic environment in 20 years.

"My job is to take on this challenge very directly," he said.

"We can't pretend that things haven't changed and we can't solve every problem the outside world throws at us what we can do do we will. The government will take every decision to maintain economic activity, to encourage new investment and above all to grow jobs. This is the key to all our work.

"Above all, our job is jobs."

He stressed the need for those jobs to be outside the public service, and for Canberra to be affordable for people on middle and low incomes.

"I don't want this to be a city where the only work is white collar and by public servants; we must never become a no-degree, no-start town," he said, signalling affordable housing as a priority. At one stage when he was a child his family had moved almost every six months through short-term rentals, making him no stranger to the pressures of finding affordable housing in a high-income city. He would use design, policy and tax reform to keep maximum downward pressure on cost of housing.

Asked later for specifics about how he would create jobs, he pointed to moves already in place to phase out stamp duty for commercial property sales, build a new hospital at the University of Canberra, attract international flights, including better links to New Zealand, and bring more international students. He would have more to say about accelerating the initiatives in the coming weeks, he said. While the international flights have not so far eventuated, Mr Barr said he expected movement in 2015 with the turnaround in aviation.

Liberal Leader Jeremy Hanson nominated for the chief ministership in Thursday's Assembly ballot, insisting Mr Barr did not have a mandate.

He had no mandate to shackle the territory with light rail, looking to cost 20 times the amount Labor took to the last election. If the full cost had been put to voters in 2012, the outcome would have been different, Mr Hanson said.

If the full extent of the increase in rates had been put to the last election, the result would have been different. And if it had been known before the last election that Mr Barr would be chief minister and Simon Corbell his deputy, the vote would also have been different.

Mr Hanson said Mr Barr had presided over an explosion in debt and deficit. His vision was to tax the family home and build a $1 billion tram, the Government's figure is just shy of $800 million, that nobody had voted for.

He said Mr Barr had got just 4.2 per cent of the vote at the last election. Every successful Liberal in the electorate, and one who had missed out, had polled higher, as had Greens candidate Caroline Le Couteur, he said.

Greens Minister Shane Rattenbury retorted that Mr Hanson had not gone into the last election as leader and yet had seen fit to nominate for the chief ministership.

Mr Hanson's analysis also ignored the enormous first-preference vote that went to Katy Gallagher in the same electorate.

Mr Barr said nothing could be more humbling than to follow Ms Gallagher as Labor leader.

"Few people have left this Assembly better liked and more respected than when they arrived and you are one of the few," he said.

"You have been a great leader ... You are a Labor hero."