Mr Swan said cabinet strongly believed that FuelWatch would help working families get the best deal at the petrol bowser.

"We took the advice of the consumer watchdog, the ACCC, (Australian Competition and Consumer Commission) and the Petrol Commissioner very seriously because they are the experts when it comes to pricing in this area," he told ABC radio.

"We have a full and frank exchange in a cabinet process. All ideas are tested. And on this occasion we went with the advice of the consumer watchdog which is the expert in the area.

"It is no secret that not everybody agreed with the policy decision. There is nothing unusual about that, nothing unusual about a diversity of views. That happens in a healthy cabinet debate."

Mr Swan said the government welcomed a diversity of views and it was not uncommon for diverse views to come from departments which might not hold the same position as their ministers.

But what mattered in the end was that all views were contested and a decision taken in the best interest of the nation.

"On this occasion ministers strongly backed the FuelWatch scheme because it has worked on the ground in WA and it will work right across Australia," he said.

Under the FuelWatch scheme which the government proposes to roll out across Australia, service stations will have to nominate a fuel price which will be fixed for the next 24-hours.

A leaked cabinet documents revealed Prime Minister Kevin Rudd's own department cautioned that FuelWatch could lead to "a small overall price increase" in the pump price.

But Mr Swan said the cabinet strongly backed FuelWatch because it had the capacity to make the market more competitive and to give knowledge to consumers.

"And in this market knowledge is power," he said.

"What I am saying is that we took a decision in the national interest."

Mr Swan said the leak, the second cabinet document leak this week, would be investigated.

"The law has been broken. Cabinet documents have been leaked. The normal procedures will click in and of course it will be investigated," he said.

AAP