A message to politicians: thinking you can bring down the petrol price is wishful thinking.

Jacinda Ardern's announced more powers for the Commerce Commission to probe petrol companies, claiming their margins have more than doubled in the last decade.

Representing the trucking sector, the Road Transport Forum says that's political posturing.

Chief executive Ken Shirley told Tim Dower outside taxes, the price rises are due to issues outside of our control - the dollar, geopolitical issues, and the international oil price.

"The previous Minister Judith Collins started a big inquiry, Megan Woods when first elected said she did a big inquiry, politicians can't jaw bone done market prices."

He said almost everything we buy is moved on a truck at some point, so fuel prices have the potential to affect the price of everything.

"Transport operates have no option but to pass on fuel costs direct to the customers for everything you can think of, fuel increases are very inflationary from an economic perspective."

LISTEN ABOVE AS KEN SHIRLEY SPEAKS WITH TIM DOWER