Ms Murphy made the revelations as she hit out at the ongoing delays to the State’s investigation into a series of controversial transactions by IBRC, saying if the problems are not overcome, “you can never, ever have another inquiry of this type”.

Ms Murphy said at the height of the Siteserv-IBRC controversy in April that she and her colleagues became concerned their phones and other equipment were under surveillance.

Ms Murphy said that, after taking “prudent” advice “on a range of different things, including our phones” from a number of independent IT and security experts, whom she declined to name, it was decided to resort to drastic measures.

From April, Ms Murphy and other officials began using “throwaway” mobile phones to contact individuals helping them with their inquiries in a bid to keep their identity confidential.

The decision was made at a time when the Siteserv/IBRC controversy led to a short-lived constitutional crisis following revelations made by Ms Murphy under Dáil privilege.

She confirmed the security measures are still being used “from time to time” eight months on, due to the continuing failure by the State to get to the bottom of the Siteserv row.

“What we did was we took some advice on a range of different things, including our phones. Look, it was prudent that we took some advice, I won’t be behind the door,” said Ms Murphy.

“We took some advice, we had some little throwaway phones where if we were making contact with people we were making sure to protect the people who we would talk to.

“We used them from April. We still have them just from time to time, but we’ll use third parties if we’ve got to. We were acutely aware that anyone who talked to us talked to us very confidentially, people who wouldn’t really want to be named.”

Asked who provided her with the advice, Ms Murphy said: “We got it from several sources and I really don’t want to go further than that. It was just prudent to consider those kind of things.”

The Siteserv/IBRC controversy has dominated the political agenda for almost a year. When a commission of inquiry was set up on June 3, Finance Minister Michael Noonan gave assurances that the investigation would be completed before the general election and was not being used to block further Dáil debates on the subject which were proving damaging to the Coalition, and Fine Gael in particular.

Brian Cregan, the judge overseeing the inquiry, last month said it would take years to complete due to serious legal and privacy issues.

Over Christmas, the judge announced he was suspending the investigation until after the general election due to the ongoing legislation issues involved.

Ms Murphy said she does not want “something that’s going to go on forever, that’s going to cost a fortune”.

However, she stressed that if the issues blocking the investigation are not “overcome”, Ireland “can never, ever have another inquiry of this type” — a situation she said will “be a removal of a type of oversight” to prevent future scandals.

Hitting out at the problems facing the inquiry, she added: “I don’t think the political will was ever there to do it before the general election.”