Justice Minister Michael Keenan was reacting to reports by Fairfax Media this week that Hells Angels gang members had allegedly defrauded millions of dollars from a diesel rebate scheme.

It was further revealed that another gang, the Rebels, was alleged to have used RAAF fuel supplies in its own excise scam.

Tax Office investigators believe federal law-enforcement agencies have failed to follow up on compelling evidence of a national network of fraud, involving up to 50 haulage firms, against the multibillion-dollar subsidy scheme.

But Mr Keenan said the government was determined to stop outlaw motorcycle gangs making money from illegal activities.

''It is not appropriate to comment on the specific issues raised in the media as these are operational matters,'' the minister said in a statement on Wednesday.

''However, the government is determined not to let bikies profit from their illegal activity, and we are taking these allegations very seriously.''

The office of Shadow Attorney-General Mark Dreyfus did not respond to requests for comment.

The Fairfax investigation found that under the scam, which allegedly generated millions of dollars, fuel subsidy claims were submitted to the Tax Office – sometimes under fake names – claiming generous Commonwealth rebates for diesel to run fictitious trucks owned by companies that exist only on paper.

Tax investigators even believe Victorian bikies had control of a post office in a country town in the state, giving them free rein to use the post office boxes under false identities without arousing suspicion.

In an unrelated case, a firm linked with NSW-based Rebels club members is accused of using aviation fuel from the RAAF’s strategic reserve to blend with diesel that was then sold to unsuspecting farmers and other rural businesses.

Mr Keenan said moves to bring the ATO into investigative taskforces with other crime-fighting agencies were aimed at breaking up bikie-related illegal activities.

''We have set up dedicated strike forces in Queensland, NSW, Victoria and Western Australia as part of the National Anti-Gang Squad,'' he said.

''These bring together state agencies and a range of federal agencies – including the Australian Taxation Office – to fight serious and organised crime.

''These squads are supported by intelligence from the Anti-Gang Intelligence Co-ordination Centre, which has been set up in the Australian Crime Commission.''