An examination of judgments registered against a group of tax defaulters by the Revenue showed the majority were self-employed and professional people who accumulated tax arrears for between 10 and 20 years, while others had never paid income tax.
Mr John Purcell's report said a group of about 1,249 mainly professional and self-employed individuals had £58 million in tax registered against them in the period examined, between 1990 and 1997.
About 90 per cent of the individuals who received the judgments did not make a settlement with the Revenue and some of the arrears remain outstanding.
The report said the group had "accumulated unpaid arrears for considerably long periods" and "some in fact have never paid tax". It stated that some of the defaulters are still in their professions and businesses.
Mr Purcell did not quantify the number of professionals and self-employed who never paid income tax, but he strongly criticised the Revenue's performance in pursuing the defaulters.
He wanted to know why "the Revenue compromised on legally-enforceable debts".
In his analysis of the 1,249 judgment mortgages (where the Revenue takes possession of an individual's property until they discharge their tax debts) Mr Purcell stated several reasons for the "compromise".
Among them was the Revenue's decision to accept settlements from defaulters below the amount of the judgment registered against them. The Revenue also reduced the tax liability to agree with totals already paid. The report also said there were cases where no payment was made and "tax assessments for all years in arrears were reduced to nil".
The Revenue also found that because the charged property was owned by somebody other than the taxpayer, usually somebody by the same name or a close relation, it could not proceed.
The report stated that despite advice from the Revenue that they should avail of the 1993 tax amnesty to clear their arrears, the individuals did not respond.
It is also likely, "despite the incentives provided", this group did not avail of the 1988 amnesty, said the report. They also refused to respond at any stage of the enforcement process, it added.
The Revenue was asked to respond to the charge by Mr Purcell that it had "compromised on legally-enforceable debts".
A Revenue accounting officer said: "The Revenue has always recognised that there were problems and difficulties in their enforcement of collection." The officer said that enforcement generally was hampered by the scope for taxpayers to appeal assessments, delaying the finalisation of a tax charge for years.
"Notwithstanding the beneficial effects of the measures taken, some of the older liability was based on unreliable estimates," the officer added.
The officer said this was not surprising because the practice was often to overestimate liability in order to "elicit a response".
"In some cases it has emerged that trade ceased earlier than our records show, so that the liability for some tax periods is actually nil".
The officer denied that the Revenue had advised people who had judgments registered against them to avail of the tax amnesty of 1993. The officer added that a "thorough check of all of the cases would be required" to see if any individual was advised to avail of the 1988 amnesty.
The officer said another problem the Revenue experienced was that in the majority of cases "the mortgage is on the family home and the taxpayer no longer has the means to pay the full amount for which the mortgage was registered".
In addition, the officer said it was often the case that the taxpayer had no means except a retirement pension and simply wished to have his or her home unencumbered in their late years.
The tax amnesty of 1993 was also said to have caused "disruption" of the Revenue's attempts to act on the liability.
The officer concluded by stating: "Most of the shortcomings identified in the use of judgment mortgages are historical in nature and have been corrected by Revenue as part of the ongoing development of the collection and enforcement processes."