We don't want, and we shouldn't need, another expensive tribunal. A scandal-weary population is right to expect speedy and comprehensive answers from AIB, the biggest bank in the country, and from the Revenue Commissioners.

This mother of all scandals - effectively that there were two tax systems operating in the 1980s and early 1990s - will provide the acid test for the privileges and compellability legislation recently enacted by the Oireachtas.

The Public Accounts Committee may send for papers and persons. Thanks to the investigative work by Magill we know that papers and records are extant. Given the prominence of the people who decorate the notepaper of Allied Irish Banks, they can hardly refuse to appear before the committee.

Neither the banks nor the Revenue Commissioners should underestimate the fury of tax-compliant citizens at the staggering scale and the seemingly benign tolerance of the evasion involved.

On April 28th the distinguished former chairman of the Revenue Commissioners, Cathal MacDomhnaill, appeared before the Public Accounts Committee on this same issue. For hours he failed to answer the members of the committee adequately. His shield was confidentiality.

The tax affairs of the citizen were confidential.

That's fine.

The Revenue Commissioners were independent.

That's fine.

I have no doubt that Mr MacDomhnaill was motivated in his evidence to the committee by the need to assert these principles. However, it ought not to be acceptable to the Oireachtas that the privileges of confidentiality and independence become a shield that risks being seen as a cover for grave lapses or deficiencies in the tax collection system.

The members of the Public Accounts Committee will be in no mood to indulge a similar performance by the new chairman, Mr Dermot Quigley, when he makes his first appearance before the committee tomorrow. Mr Quigley is the latest in the line of honourable and dedicated public servants to hold this position of trust for the Irish taxpayer. He must recognise that the discreet patriotism of the 1950s is not the way to address the scandals of the 1990s.

It is not good enough that members of the Public Accounts Committee are obliged to read in Magill the answers to questions side-stepped by his predecessor six months ago. Could it be that senior Revenue personnel don't fully appreciate the anger of ordinary taxpayers at the revelation that there has been a parallel tax regime in operation for the great and good and the crooks in our society. It is more likely, I feel, that Revenue believes that these "lapses" should be sorted out behind closed doors.

There is a cosy tone to the correspondence revealed to Magill that will not be readily recognisable to the struggling taxpayer doing his or her best to meet their lawful tax dues. Given the sheer scale of what has been going on behind closed doors, these "settlements" are no longer acceptable.

What possible considerations could have justified writing off £86 million - in reality a great deal more with penalties and interest - for the biggest bank in the country? It seems that the entire scale of the scam was not exposed to the Revenue Commissioners.

Similarly, it is evident that the Revenue took no steps to establish the scale of tax evasion either in AIB or in the other financial institutions. The initial defence of AIB ought not to be forgotten: it was that the practice of facilitating tax evasion was "industry-wide".

All of this was going on for more that a decade after hundreds of thousands of people marched throughout Ireland against high personal income taxes and in favour of broadening the tax base. These same people now want to know precisely what the considerations being weighted by the Revenue Commissioners were when they agreed to such a huge write-off for one of the largest companies in Ireland.

If, as is now being suggested, to refuse the write-off would have caused "disruption in the market for government bonds", Mr Quigley will have to speak frankly on this aspect to the Public Accounts Committee. If this was a consideration, how much validity did it have and how much is the product of fevered spin-doctoring now going on?

Nobody on the committee wants to know the identity of the beneficial owners of the 53,000 bogus accounts. But we do want to see accountability for the systems being operated by the Revenue Commissioners. We want to know how much the Revenue knew about the scale of the parallel tax system being operated by AIB. We want to know whether at any stage representations were made to the Revenue on behalf of AIB by any politician. We want to know if the Revenue Commissioners have made similar settlements with other banks or financial institutions.

The public has a right to know the answer to such questions, and no reasonable invocation of the duty of confidentiality can obviate the necessity to answer these questions.

These deals are unacceptable to the Revenue's own officials who have used trade union platforms over 20 years to inform the public and advocate many of the changes now implemented. They are unacceptable to the Comptroller and Auditor General who has highlighted his concerns about the "settlement culture". They are unacceptable to the great bulk of ordinary taxpayers who do their best to pay their lawful taxes.

The Moriarty tribunal is required to make recommendations "for the protection of the State's tax base from fraud or evasion in the establishment and maintenance of offshore accounts, and to recommend whether any changes in the tax law should be made to achieve this end". This requirement, won by the Opposition during the negotiations for the terms of reference for Mr Justice Moriarty, is now an immensely valuable one.

Secondly, the examination directed to begin tomorrow by the Public Accounts Committee chairman, Mr Jim Mitchell, should, at a minimum, provide interesting raw material for the Moriarty tribunal. The unexplained shutdown of this story by most sections of the media, about which I wrote at some length in Magill in May 1998, no longer pertains. I wrote then that "having broken this staggering story (Liam Collins, Sunday Independent) . . . the media have yet to prove that the story is not too big for them".

Whatever about the power of the vested interests involved, I hope I will not be proved wrong.