A whistleblower has alleged investigators at the banking inquiry dined with a participant a few days before its representatives appeared before the committee.

An investigator, who worked with the inquiry until recently, has submitted an 82-page document under the Protected Disclosures Act claiming wrongdoing at the committee.

The correspondence, which was sent to some members in April, makes a series of allegations about the investigation team hired by the inquiry.

The Irish Times has learned one of the claims made is that a senior investigator dined with one witness "days before the representatives of the participant appeared before the joint committee".

It is unknown at this stage who the participant or its representatives are.

The whistleblower also alleges preferential treatment was given to the Central Bank, the Department of Finance and, to a lesser extent, the National Asset Management Agency (Nama).

The document alleges the provision of false information to the committee and the inappropriate management of potential conflict of interests by lead investigators.

Inappropriate

It claims there was inappropriate engagement with some participants before committee hearings.

The whistleblower, who cannot be named, also alleges attempts by investigators at the inquiry and regulatory authorities to exclude a department whistleblower from attending a public hearing of the committee.

In their disclosure, the investigator said the claims were legitimate and warranted investigation.

The whistleblower had contacted chairman of the inquiry Ciarán Lynch, Sinn Féin’s finance spokesman Pearse Doherty, Labour Senator Susan O’Keeffe and Socialist TD Joe Higgins with the claims in April.

An internal investigation was launched by the Houses of the Oireachtas that month and the findings were issued to the complainant in May.

The allegations came to light last week when the whistleblower contacted other members of the committee.

The whistleblower now says their pay has been reduced since the claims were brought to the attention of the media.

In a letter to members last Friday, they said they intended to attend the offices of the committee today and return to their duties.

The investigator said they wish to complete the work they had prior to making the protected disclosure, including challenging redactions by the Central Bank to the inquiry.

In the letter, the whistleblower said attempts to cut their salary are a breach of the Protected Disclosures Act.

‘Abject failure’

The correspondence was also sent to Minister for Public Expenditure and Reform Brendan Howlin because of the "abject failure" of the Houses of the Oireachtas to adhere to the law.

A spokeswoman for Minister Howlin said he was on leave and had not seen the correspondence sent to him.

Fianna Fáil Senator Marc Mac Sharry said there is a need for an independent investigation. “It cannot be conducted by anybody internally. These are serious allegations that require serious scrutiny. “

The committee meets in private on Tuesday.