Traffic congestion in Auckland could be costing nearly $2 billion a year and is having a big impact on the city's productivity, according to a new report.

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The report has prompted renewed calls for politicians to get cracking on solving the traffic problems in the country's biggest city.

Commissioned for the Employers and Manufacturers Association (EMA), the report underlines what most of Auckland knows - that journey times are getting longer and transport firms are having to expand their fleets to the work done.

David Aitken, the chief executive of National Road Carriers, which represents large and small transport firms, said the problem had been getting worse for years.

Mr Aitken said over nine years, the number of crosstown trips possible for transport firms in a working day had halved to slightly more than three.

"We've seen that change in just the last three years. One of the journeys they put (in the report) is Pakuranga to the CBD, which in just three years has increased by 21 minutes, or 45 percent, and it's going to get worse," he said.

He said trucking firms in other regions were recruiting Auckland drivers with the lure of less stressful work, and future growth would make things worse.

"The freight task is predicted to grow 60 percent between now and 2030. So when you've got less productive journeys, and you're struggling to get drivers to do them, you're heading for disaster."

In the report, consultants NZIER estimated the cost of congestion on weekdays as between $0.9 billion and $1.3 billion a year.

The goal of always having free-flowing traffic, which NZIER admitted was unrealistic, would save Auckland $1.9 billion a year.

Employers and Manufacturers Association chief executive Kim Campbell said the problem had grown beyond just being about transport, to one of productivity.

"Here we see in one report, very clearly articulated, one single thing that we could do to make almost a 30 percent difference to productivity across the entire economy, is do something about congestion," said Mr Campbell.

Auckland Council and the government were working on devising the list of projects the region needed, and when they might be built, as well as new ways of funding, such as road tolling.

Stephen Sellwood, from the construction lobby group Infrastructure New Zealand, said the recently-opened Waterview Tunnel took more than two decades to realise, which did not bode well with the rapid population growth Auckland faced.

"Another million people, so if you can contemplate that sort of painstaking decision-making process to meet that huge demand, we are going to be in huge strife," he said.

"If it's costing us $1.5 to $2bn a year, today costs us in the future."

Economists from the Auckland Council have taken their own look at possible solutions. Chief economist David Norman said many businesses could make changes, such as shifting their working hours, or moving closer to where staff lived.

NZIER said it hoped its new estimates would be a clarion call to lift research and policy-making.