My Senate colleague Nick Xenophon and I were at Marie El-Khoury's Blacktown BP service station in western Sydney this morning to help motorists fill their vehicles with cut-price fuel.

Marie had dropped the price to 49.9 cents for one hour to highlight the fight she has with the major oil companies.

Independent petrol sellers are asking us for help to force the Federal Government to investigate claims of "anti-competitive" and predatory pricing.

How can the independents make a living if Coles and Woolworths can sell petrol at cheaper prices than the independents have to pay for their supplies?