The tax inspectors who dealt with negotiations on AIB's DIRT liability in 1991 are to be called before the Dail Committee of Public Accounts.

Meanwhile the former AIB internal auditor, Mr Anthony Spollen, is likely to accept an invitation to appear before the committee and appears likely to defend his £100 ,million estimate for the amount of tax outstanding on bogus non-resident accounts.

The £100 million figure was based on data supplied by the former group taxation manager Mr Jimmy O'Mahony, who is also being invited to appear before the committee.

In what the chairman of the committee, Mr Jim Mitchell, described yesterday as an "unprecedented" move, the committee has summoned the four senior inspectors involved to appear before it.

Other banks and financial institutions may also be asked to appear to enable the committee to investigate AIB's claim that the use of bogus non-resident accounts was endemic in the industry in the late 1980s and early 1990s.

To this end, transcripts of this week's evidence to the committee have been circulated to a number of central figures - including the former AIB chairman, Mr Peter Sutherland; its former group taxation manager, Mr Jimmy O'Mahoney; and its former group internal auditor, Mr Anthony Spollen - who are also being invited to appear. Sources close to Mr Spollen say that he is likely to accept the invitation.

It is hoped that Mr Spollen and Mr O'Mahoney - both of whom received the invitations yesterday - will be able to appear before the committee on Wednesday.

The four tax inspectors may throw light on the conflict between the bank and the Revenue over whether AIB was granted an effective "amnesty" on tax arrears due before 1991 on bogus non-resident accounts.

All four attended a key meeting with AIB in February, 1991, at which, the bank claims, Revenue offered "an amicable solution" to the problem of unpaid DIRT - estimated by Mr Spollen at the time to total £100 million - on these accounts.

The bank claims it was given several months to regularise its non-resident accounts and Revenue agreed not to pursue arrears going back to 1986, when DIRT was introduced.

The Revenue chairman, Mr Dermot Quigley, who is to be called before the committee again on Wednesday, has denied there was a deal and says the bank did not supply the full information at the time.

The inspectors - only one of whom, Mr D.A. Mac Carthaigh, has been named before the committee - are being put on notice to be available to the committee from October 27th.

The committee normally calls as witnesses only the most senior officers of whatever State agency it is investigating.

Mr Mitchell said the committee's first duty in this inquiry was to call to account the Revenue Commissioners. In this case, that also required investigating whether the banks had carried out their tax collecting duties in accordance with the law.

Mr Mitchell is to hold a case conference on Monday afternoon with the Comptroller and Auditor General, Mr John Purcell, committee staff and legal advisers to examine how the investigation should proceed from here.

In the meantime, legal advice is also being taken on how the committee can best pursue its requirement for the Revenue and AIB to supply documents concerning their 1991 discussions.

The committee has power to seek documents and ask witnesses to attend, but they cannot be compelled to appear in relation to taxation matters. In other cases, their attendance can only be compelled - and the production of documents ordered - by resolution of the Dail.

The committee meets on Tuesday, probably in private, when it is likely to focus on the next steps in its investigation. It also meets at 9.30 a.m. on Wednesday when further witnesses, including Mr Quigley, may be called. Further meetings have been scheduled for Wednesday and Thursday, October 28th and 29th.

The AIB chief executive Mr Tom Mulcahy and senior officials of the bank are also likely to be recalled. The question of inviting other banks and financial institutions is being considered, Mr Mitchell confirmed.

One committee member, Mr Pat Rabbitte, said yesterday he believed such a move was inevitable. "We are being told this practice was industry-wide and I think that's something we will have to have a look at," he said.

The committee's dilemma is that it must be seen to be fair to AIB by not targeting one institution, but at the same time does not want the inquiry to become unnecessarily wide-ranging.