Mr Barr said "new vehicles" would drive infrastructure and infill projects over the next four years, with the Land Development Agency focusing more fully on greenfields estates. He mentioned the plan at a leaders debate hosted by the ACT Property Council, but gave no details. His office said more information would be released during the election campaign.

The government envisages Northbourne Avenue will house as many as 45,000 extra people with the sale and redevelopment of government buildings and public housing.

Debate moderator Annabelle Pegrum put to the leaders that the Kingston Foreshore project was yet to be completed after 20 years, the Kingston arts precinct plans were yet to be finalised, years had been spent planning the Yarralumla brickworks, and the future of the City to the Lake project was uncertain. She said the government had lost momentum on affordable housing in the past decade, with no specific targets for affordable housing of particular types or in particular locations.

Mr Barr said housing affordability was a national problem with causes well beyond the ability of the ACT to influence, including negative gearing and low interest rates. But he would continue cutting stamp duty, which was already helping, increase land supply – both infill and greenfields suburbs, and make land available for community housing.

Mr Hanson said housing affordability was the Barr government's greatest failure. It was a "disgrace" that low and medium-income earners were now priced out of the housing market.

The Land Development Agency had failed as a developer and a Liberal government would reform the agency and its land release program. The job should be left to the private sector, he said, pointing to the $1000 a square metre cost of land in Throsby compared with $450 a square metre across the border in Googong.

The lease variation tax strangled new development and a Liberal government would repeal the tax in the town centres, which would encourage more affordable housing in places where the elderly and the young wanted to live, he said. He would also stop the shift of tax from stamp duty to rates.

Mr Hanson said Canberra was at a crossroads, with the outcome of October's election set to shape the city for generations to come – chiefly because light rail would change the fabric of the city. He reiterated his promise to scrap the project, saying it was old and inflexible and would force rates increases for years to come. Transport should look to future technologies, he said.

"Driverless vehicles powered by electricity and hydrogen should be the norm, far better that the tram."

Mr Barr said the only revenue-raising options the government had were to tax labour, capital or land. Labour was mobile and should be lightly taxed. Capital was highly internationally mobile, which was why the government was cutting payroll tax. Land tax was the most simple, fair and efficient way for state and territory governments to raise revenue, he said. It was the least distortive and the most predictable tax.

Mr Barr hit out at Mr Hanson as "big-spending" Jeremy in some debates and "small-government" Jeremy in others. "This guy will promise all sorts of things," he said.