Oil giant Shell Australia has reignited big business' war of words with the Australian Competition and Consumer Commission.

Coming on the heels of Caltex Australia's harsh criticism of the competition regulator last week, Shell Australia weighed into the debate by describing the ACCC's behaviour in administrating its legislation as 'cavalier', 'inappropriate' and 'illegitimate' in a submission to an inquiry looking into competition law.

In its submission, Shell said the regulator needs to administer its activities with greater 'objectivity and detachment' or be supervised by a body that can.

"The commission has, over an extended period, consistently undermined public confidence in big business by its conduct, most particularly by evocative and provocative press statements and by inflammatory conduct such as the recent raids on oil company premises," the Shell submission says.

Shell's submission argues strongly against a new effects test in competition law and proposes a number of amendments, including a more efficient process to assess mergers.

And following its recent experience with a well-publicised raid of its premises by ACCC officials, Shell recommended a narrowing of the commission's powers to enter sites and seize documents.

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