And the office consolidation that sparked industrial strife in Sydney and Brisbane is set to intensify as workers in other capitals are soon to be on the move, according to one of the ATO's unions.

The ATO confirmed on Wednesday that it was facing ''difficult decisions'', but took aim at the Australian Services Union, saying its message to members was ''disappointing'', ''disrespectful'' and included personal attacks on senior Tax Office staff.

In a strident letter to its ATO members sent out on Wednesday, the union alleged that the Tax Office was in ''turmoil'' and that many more of its staff could be forced to move to new workplaces.

ASU organiser Jeff Lapidos said the closure of offices at Southport in Queensland and Hurstville in Sydney, and looming moves from central Sydney to Parramatta, which have been bitterly received by workers forced to move, will be repeated at other sites around the nation.

''[The] decision to move from Sydney to Parramatta makes it doubly clear such consolidations will be a feature of ATO 'planning' over the next year or two,'' Mr Lapidos wrote to his union's members.

''This is likely to affect all major ATO offices around Australia. People will be expected to move in Melbourne, Sydney and Brisbane.''

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He also predicted changes to workplaces in Adelaide, Perth and Hobart. The official said Taxation Commissioner Chris Jordan, pictured, was preparing to break with decades of tradition and move his main base of operations from Canberra to Sydney's central business district.

''It is difficult to predict what will happen with National Office functions in Canberra, given the Commissioner['s] interest in working from Sydney and seems to only want to go to Canberra if he is required by his masters,'' Mr Lapidos wrote.

The cash-strapped ATO is cutting 900 jobs this year in an effort to balance its books. It is also undertaking a program of consolidation around the country after it reached a point where nearly 5000 desks were sitting empty in its office buildings.

The Canberra Times revealed this month that a new suite of offices is being built for Mr Jordan and senior deputies on the top floor of the Tax Office's Latitude East building in Sydney's CBD with the 50 or so rank-and-file staff displaced by the work likely to be sent to Parramatta.

An ATO spokeswoman said on Wednesday the office was disappointed with Mr Lapidos' approach to his message to members.

''Throughout this process we have consulted with staff and with unions in a genuine, professional and courteous way,'' she said. ''It is disappointing to see the ASU reporting on good faith interactions in a disrespectful way, including personal remarks about the conduct of the ATO Commissioner and Executive.''