Mr Justice Flood has rejected a submission from Mr Ray Burke's legal team that the tribunal was using unfair procedures against the former Fianna Fáil minister.
In a written response Mr Justice Flood said: "Satisfied, having regard to my terms of reference, that matters in respect of payments to Mr Burke and matters concerning the source and destination of a particular portion of his income are properly the object of my inquiries and that the evidence proposed to be lead in relation to them is admissible.
"I am also satisfied that the admission of this evidence does not in any way infringe the rules of fair procedures.
"I reject the suggestion that the admission of any part of that evidence would amount to bias."
Mr Aidan Walsh SC, for Mr Burke, said yesterday the tribunal should not publicly hear any evidence on the financial affairs of Mr Burke given he had co-operated fully and had already provided so much information.
It was unfair of the tribunal to trawl through more than 20 years of Mr Burke's financial affairs without first producing any allegations. "The cart is being put before the horse," he said.
Mr Patrick Hanratty SC, for the tribunal, described Mr Walsh's submission as "astonishing" and said it was a "fundamental misunderstanding" of the nature of a public inquiry.
He agreed that Mr Burke's financial affairs were private but said they could not be ignored if they were relevant to the tribunal's investigations.