Speaking at a business lunch in Melbourne last week, the managing director of the Commonwealth Bank of Australia, David Murray, accused the ACCC of "corrupt administration" of the Trade Practices Act.

He also suggested that Caltex Australia should sue the competition regulator over the way highly publicised raids in April were handled. Mr Murray accused the ACCC of setting up the media to take photographs of ACCC staff coming out of Caltex offices carrying boxes "full of something".

Mr Murray's attack came as Caltex boss Dick Warburton stepped up his attack on the ACCC at a function in Perth, saying it should not be allowed to write its own search warrants, a power it shared only with the Taxation Office.

However, head of the ACCC, Professor Fels, hit back at his critics by saying big companies were trying to distract attention from issues of substance.

"Big banks, big retailers, big oil are all ganging up in an effort to discredit and emasculate the ACCC, which they resent because of the protection it offers small business and consumer," Professor Fels said.

"Caltex could challenge the legitimacy of the ACCC's investigations - but they have instead chosen to run a public relations campaign."