The Oireachtas Banking Inquiry whistleblower is considering legal action in connection with the findings of a review conducted recently into allegations they made of improper conduct by the inquiry's investigations team.

It is understood that the whistleblower, who is a lawyer, considers the report to be defamatory of their professional reputation.

"I am taking appropriate legal advice," the whistleblower said in a hard-hitting statement to The Irish Times.

The whistleblower “categorically” refutes the conclusions of the report and has “grave concerns” about the manner in which the review was conducted.

The whistleblower also takes issue with the language used in the report.

The report has yet to be published but it believed to have concluded that there is no substance to the allegations. It is understood that the report has found that robust processes were in place to deal with conflicts of interest.

The report was compiled by Senan Allen, senior counsel, on behalf of the Houses of the Oireachtas Service, which employs the whistleblower.

In April, the whistleblower made allegations against certain members of the investigations team of the banking inquiry. They claimed that the Central Bank of Ireland and the Department of Finance were give preferential treatment as the investigations team went about its work.

It was also claimed that a number of undocumented meetings took place with the Central Bank and that certain information was allowed to be redacted. Mr Allen was charged with investigating the allegations. He declined to comment when contacted by The Irish Times.

No comment was available from the Houses of the Oireachtas service, which manages the day-to-day operation of the Dáil and Seanad.

The whistleblower joined the inquiry’s investigation team in January 2015 to support the work of the 11-member committee of TDs and senators.

The whistleblower said they accepted this role for two reasons: the scale of the financial crisis and its long-term impact on the country; and the fact that their experience in the financial services industry would help the inquiry in a “meaningful way”.

“My decision to come forward as a whistleblower was not taken lightly. My reason for doing so is that I had, and continue to have, serious concerns about the manner in which the banking inquiry is being conducted,” the whistleblower said.The whistleblower claims to have been isolated as the single complainant despite alleged evidence that three other investigators had expressed concern about how the inquiry investigation was being conducted.