Minister for Finance Michael Noonan has stressed the importance of ensuring evidence is not "contaminated" in relation to the investigations into Anglo Irish Bank.

He was responding to a question as to why the bank's former chairman Alan Dukes had not conducted his own investigation in 2009 and 2010.

Mr Noonan said: "You could see what could happen in court if there was ready and free access by a lot of people to evidence that it would be produced subsequently."

He added: "The guards are the people who investigate crime. The guards have a statutory right to gather evidence. Other people should not be mucking around in Garda business."

Mr Noonan added that he had written to the chairman of other banks alerting them to the possibility that recordings could be required for a possible banking enquiry.

He also said he was not aware whether the material on the Anglo tapes had been given to civil litigants against the now defunct bank, adding that the special liquidator of IBRC was investigating whether the leaks could have come from the bank or KPMG, which is running the liquidation process.

In a written reply to a parliamentary question from Sinn Féin's Pearse Doherty, Mr Noonan reveals that in 2010 the Garda Bureau of Fraud Investigation under court order obtained electronic and other documents related to 18 employees of Anglo Irish Bank whose telephone lines were recorded.

Around the same time, the Nyberg Banking Commission was provided with large volumes of material for its investigation.

The minister does not say if the commission received the Anglo tapes.

The tapes were disclosed in the Irish Independent in recent weeks.

Mr Doherty now wants to know if the Nyberg commission was given the full information about Anglo.

Mr Noonan also says that the Joint Special Liquidators appointed to wind up the IBRC have written to all parties whom they know had access to the tapes, including civil litigants, advising them that they are taking the leaks very seriously.

The liquidators intend to appoint an independent party to investigate if the leak came from IBRC or KPMG.

Mr Doherty said this morning "serious questions" have been raised given Mr Noonan and the Central Bank were unaware until recently that the telephone recordings existed.

Speaking on RTÉ's Morning Ireland, Mr Doherty asked whether the public interest directors on Anglo Irish Bank’s board were aware of the tapes, and if so, why they were not brought to the attention of the Department of Finance.