Voters who supported Labor and the Greens at the 2012 territory election understood a light rail line for Canberra was central to both party's policies, Capital Metro Minister Simon Corbell said on Wednesday.
Government members and Greens Minister Shane Rattenbury combined to defeat a motion from Opposition transport spokesman Alistair Coe calling for a delay in the signing of contracts worth about $800 million after the 2016 election.
Mr Coe argued the government was without a mandate for the 12-kilometre line linking the city and Gungahlin, due to begin construction next year.
He said Labor had only committed to spend about $34 million in September 2012, before voters went to the polls. The next election was an opportunity for the community to give their informed view, he said.
Citing media reports and a policy announcement from former chief minister Katy Gallagher, Mr Corbell said voters had understood a returned Labor government would seek to "establish the ACT's first large-scale private sector partnership to plan, finance and develop the first stage of a light rail network for Canberra".
Ms Gallagher's Capital Metro policy statement outlines $30 million in committed spending by 2015 and specifies the estimated $614 million total cost would come from a public private partnership. The government also unsuccessfully sought $15 million in funding from Infrastructure Australia for the project.
"Given that this government has been elected with light rail as a central plank of our policy, it is only right that we honour [voters'] wishes, as evidenced by their support and reflected by the members in this place, and proceed with light rail," Mr Corbell told the debate on Wednesday evening.
"The project timeframes are consistent with infrastructure projects of this size and it does not give the industry confidence if we start changing those timeframes."
Mr Rattenbury accused Mr Coe of continuing with predictable motions critical of light rail and questioned if Mr Coe had the support of his Liberal colleagues for repeated criticism of the project in the Legislative Assembly.
He accused the Liberals of trying to avoid releasing a substantive transport policy ahead of the October 2016 poll.
"Just to make this crystal clear: Mr Coe will rip up a contract that is for an environmentally sustainable public transport project, supported by the majority of the community, assessed as being positive for the city and he will make the taxpayers pay for it," Mr Rattenbury said.
"Now Mr Coe is perhaps the most vocal of all the Liberals in this place in claiming to care about the humble taxpayer and the value of their tax dollar. So its a stunning admission to say that he will force them to pay millions of dollars for nothing and at the same time condemn our city to a future without a modern first-class sustainable power light rail system."
Mr Coe last month congratulated the Victorian Labor government for its decision to pay $339 million to cancel a controversial road tunnel project signed off by the former Coalition government two months before the election.
Mr Coe said the compensation pay out was "reasonable" and could set an example for a future Liberal ACT government.
Prime Minister Tony Abbott and infrastructure lobby groups were among those to criticise the Victorian government's decision to cancel the contracts.