Taxpayers forked out millions to sell the federal government's infrastructure promises in the lead up to the May election, dwarfing spending in the previous year.
Infrastructure department officials confirmed more than $13 million was spent on advertising projects in the past financial year.
But just $272,000 in taxpayer funds went to similar advertising in 2017/18, while $64,000 was spent in 2016/17.
Labor frontbencher Murray Watt asked cabinet minister Bridget McKenzie about the issue during a Senate estimates hearing in Canberra on Monday.
"It spent $11.626 million of taxpayers' money in the three months leading up to the election - you got a pretty good return on your investment didn't you?" he said.
Senator McKenzie said the decision was based on market research indicating a low level of community awareness about infrastructure spending.
"This campaign was about informing the Australian public about spending on infrastructure in their local communities," she said.
Senator Watt noted the government spent about 60 times more money on infrastructure spending in an election year than the previous year.
"That's just a total coincidence?" he asked.
The opposition used Senate estimates to target the Morrison government's inability to deliver on its key infrastructure promises.
It also dominated question time, with Labor seeking answers as to why there had been a $5 billion underspend on roads since the coalition was elected in 2013 and asking for spending to be fast-tracked to boost the economy.
"Scott Morrison must get to work and develop a real plan for infrastructure to create jobs and improve productivity across regional Australia," Labor's infrastructure spokeswoman Catherine King said.
She pointed to construction having yet to start on 98 per cent of projects from the government's flagship Roads of Strategic Importance program, which was highlighted in the 2018/19 budget handed down last year.
Urban Infrastructure Minister Alan Tudge told parliament work had begun with the states and territories on all of the government's promised urban congestion fund projects.
"The state governments share our desire to get these projects under way as quickly as possible," he said.
Prime Minister Scott Morrison told parliament the budget included $10 billion in infrastructure spending, which was making an impact "right around the country".
Australian Associated Press