Record road spending nationwide during the past decade has been marred by large amounts being funnelled into questionable transport projects in marginal electorates, according to a damning new report.

Respected think-tank the Grattan Institute has found too much taxpayer money has been "spent on the wrong projects in the wrong places", during a period that marked the highest levels of spending on transport infrastructure in Australia's history.

Concern about pork-barrelling to win votes is set to grow in the lead-up to the federal election this year, particularly in marginal seats such as New England.

By analysing the expense of major road and rail projects against the level of demand, the institute has uncovered the nation's worst projects, including several rural highways.

The New England Highway in rural NSW is one of three major roads running through marginal seats to have government funding lavished on costly upgrades due to "political considerations", the report found.

The contest for the rural electorate in northern NSW between Deputy Prime Minister Barnaby Joyce, the sitting federal member, and independent Tony Windsor will be one of the most keenly watched this election.

The report found political considerations were "clearly a factor" in spending on roads such as the New England Highway, despite relatively low levels of traffic compared with other major routes.

"What we see is a pattern of spending that is quite politicised," the institute's director of transport and cities, Marion Terrill, said.

"Often these projects have low net benefits – or they have net costs."

The federal, NSW and Queensland governments have collectively spent $2.1 billion during the past decade on the New England Highway, which connects Newcastle to southern Queensland. That amounts to 9 per cent of all road funding for the so-called national network outside the country's capital cities.

In fact, more taxpayer money has been directed to the New England Highway in the past 10 years on a per-vehicle-kilometre basis than the Pacific Highway, the most heavily used in the country, the report found.

In the same period, the number of trucks using the New England Highway dropped, and rose on the Pacific Highway. The latter offers drivers a shorter and faster trip between Sydney and Brisbane.

The institute cited major roads between Colac and Geelong in Victoria, and Bell Bay and Launceston in Tasmania, as other examples of highways within or close to swing electorate seats that have had expensive upgrades.

About $435 million has been forked out during the past decade for an 89-kilometre stretch of the Princes Highway from Geelong to Colac that runs through the increasingly marginal federal seat of Corangamite.

The report also reveals higher federal funding for transport projects in NSW and Queensland – states where national elections tend to be won or lost – than states such as Victoria, which have historically had few swing seats.

The Grattan Institute said the record of successive governments' spending on roads gave people little confidence in where and how taxpayer money was used.

"Too often, political considerations come ahead of the public interest," its report says.

The institute wants state governments to commit money to transport projects only after a "rigorous, independent like-for-like evaluation" has been tabled in Parliament.

It has recommended similar arrangements for federal ministers, and believes Commonwealth funding to the states "should stick where it hits" – or where the benefits outweigh the costs.

State Labor transport spokeswoman Jodi McKay said the opposition supported the tabling of business cases for projects in Parliament.

"We have seen a worrying trend from this government of refusing to release business cases or, in cases like WestConnex, doing everything it can to avoid scrutiny," she said.

"When a government is spending billions of dollars on roads and transport projects, it has an obligation to show taxpayers that they are getting value for money."

A spokesman for Transport Minister Andrew Constance said the state government set up Infrastructure NSW as an independent body to "take politics out of the delivery of major projects", and ensure funds were directed on strategic and economic merit.

Shadow federal transport minister Anthony Albanese said Infrastructure Australia needed to be "taken seriously" to break the nexus between short-term political cycles and long-term transport projects.

"There is a structure there – we don't need to reinvent it. The problem is government will," he said.

Mr Albanese accused the Coalition government of taking money away from projects that would have had good cost-benefit outcomes, such as the Melbourne metro rail project.

However. federal Transport Minister Darren Chester said the government's $50 billion infrastructure investment program was based on "merit-based assessment processes".

Infrastructure Australia conducted cost-benefit analyses of proposals seeking $100 million or more in federal money, Mr Chester said.