The Moriarty report is expected to link the support of the former taoiseach Charles Haughey for a number of passport applications in the 1980s to a payment of £50,000 he received in 1985.
Such a finding in the report, expected to be published this week, would conflict with the late Mr Haughey's evidence that he did no favours in return for the money he received over the course of his political career.
The former taoiseach's family expects that Mr Justice Michael Moriarty will reject Mr Haughey's evidence that the 1985 payment was in return for a yearling sold to a wealthy Saudi diplomat and businessman, the late Mahmoud Fustok.
Mr Haughey took an interest in applications for naturalisation from a number of Mr Fustok's relatives and associates in the 1980s. In 1989 he directed a civil servant to naturalise a nine-year-old Lebanese girl against the wishes of Department of Justice officials.
The Moriarty report, which may be published as early as today, is expected to make adverse findings against the former taoiseach in four key areas.
As well as rejecting Mr Haughey's evidence in relation to the 1985 payment, an adverse finding is also expected against him in relation to his personal use of some of the money raised for the late Brian Lenihan's liver transplant in 1989, as well as funds from the former Fianna Fáil leader's allowance account.
It will also find that Mr Haughey incorrectly arranged a meeting between the then chairman of the Revenue Commissioners, Séamus Parcéir, and the businessman Ben Dunne, who gave Mr Haughey in excess of £2 million in the late 1980s and early 1990s.
The fact of the meeting between Mr Paircéir and Mr Dunne, and Mr Haughey's role in setting it up, was not revealed to the 1997 McCracken tribunal which investigated payments to Mr Haughey from Dunnes Stores.
At the time the Dunne family trust was contesting a £38.8 million capital gains tax bill. Mr Paircéir was involved in the case and after he retired from the Revenue was engaged by the trust to prepare a paper on the case.
The report is expected to state that Mr Haughey failed to co-operate with the tribunal, a finding that has significant implications for the late politican's estate as it may be forced to pay Mr Haughey's legal costs as well as part of the tribunal's own costs.
Mr Haughey's family is expected to make a statement once the report is published, which is likely to reject all of the adverse findings against the former Fianna Fáil leader.
The tribunal has refused to state when the report will be published, but it is now expected to be this coming Thursday at the latest.
It will be an interim report dealing solely with the issue of payments to Mr Haughey and any of his acts or decisions that may have been influenced by the payments. It will be the first report by the tribunal which was established in 1997.
Under the Dáil resolution which established it, the tribunal's report will be delivered to the clerk of the Dáil, who will then place it in the library of the Houses of the Oireachtas. Copies of the report will then be made available to the media and general public.
The publication of the report comes at a sensitive time for Mr Haughey's TD son Seán, who is seen as the front-runner to be appointed as a Minister of State tomorrow.
The Taoiseach, Bertie Ahern, is to announce the new junior minister following tomorrow's cabinet meeting, to replace Síle de Valera, who stepped down from her post as Minister of State at the Department of Education on Friday.
The Moriarty tribunal will publish further reports dealing with payments to the former Fine Gael minister Michael Lowry and any acts or decisions of his that may have been affected by payments.
Moriarty expected to criticise Haughey strongly: page 9