The Australian Taxation Office's internal police could themselves be investigated by Australian Federal Police anti-corruption officers.

There are allegations that the ATO’s crime-fighting unit abused its powers while pursuing internal threats.

It is a rough period for the Taxation Office’s Fraud Prevention and Internal Investigations (FP&II) unit, which has had to apologise for digging through one woman’s personal internet history in order to catch a totally separate person.

FP&II also faces legal action after it wrongly linked two former tax officials to a grisly Melbourne underworld killing.

It is understood that Federal Police in Canberra are looking into a complaint from an ex-taxation staffer to their anti-corruption bureau.

The staffer alleges FP&II acted illegally in an investigation of its former colleague, whom they suspected was running a hate mail campaign against a senior figure in the unit.

The ATO unit’s chase culminated in a raid at the HMAS Cerberus naval base in October 2011, when public servants armed with a search warrant burst into the man’s office and spent several hours scouring for evidence.

The unit also used its powers to gain access to weblogs of an unrelated family member, which the Australian Information Commissioner has now found was a breach of the woman's privacy,

Assistant Information Commissioner Jonathan Todd has offered an “unreserved apology” for the conduct of FP&II

The former ATO staffer who made the complaint had pleaded guilty in 2010 to unlawfully accessing the tax records of family members.

But he says he is innocent of the hate mail campaign that FP&II chased him for, and has told the Federal Police that several members of the unit committed abuses of public office in their pursuit of him, such as making false statements to obtain the Cerberus search warrant.

An Ombudsman's investigation reportedly recommended an independent review into FP&II after checking over the case, but there has been no official word on any progress.

The Information Commission has ceased its investigation into the complaint on the grounds that “the ATO has adequately dealt with the matter”, a spokesperson told Fairfax Media this week.

Meanwhile, former taxation investigators Peter Spence and Bob Hynninen say they are close to the official launch of legal action against the ATO for their wrongful implication in the killing ofMelbourne “vampire gigolo” Shane Chartres-Abbott.

The pair spent years under a cloud of suspicion after claims they accessed tax files on Mr Chartres-Abbott before he was murdered in 2003.They will reportedly accuse the government agencies of forcing them out of their jobs and implicating as suspects in the underworld- killing.