The Environmental Protection Agency (EPA) has rejected accusations of "bias" in research it commissioned into fracking.
EPA deputy director general Dara Lynott was forced to bat away scathing criticism of the two-year study project when he appeared before t he Joint Transport and Communications Committee.
Mr Lynott said: " Our role is the protection of the environment and as part of that we commissioned what we believe is world class research.
"No fracking is going to take place as part of this research. The ministries have said that no fracking is going to take place until this research is over. And, there is no guarantee fracking will ever take place."
The EPA has contracted a consortium including academics, the British Geological Survey and a law firm to examine the impact of the controversial gas extraction method on the environment and human health and compile a series of reports next year.
But the involvement of consultancy company CDM Smith has been heavily criticised.
My Lynott said: "I fully accept that there are concerns that in the past CDM Smith have been involved in advising both pro-fracking and anti-fracking governments that people would see they are in some way biased. That is not the view of the EPA.
"At the end of this will be a series of reports and data that will be open to everyone to decide whether they are appropriate; whether they are biased or not biased (and) whether they have got the facts right. We are totally open to that."
Hydraulic fracturing, commonly known as fracking, is the process of drilling down into the eart h before a high-pressure water mixture is directed towards the rock to release the gas inside.
CDM Smith has advised on exploratory gas extraction projects in Poland and Germany, the committee was told.
However, Fianna Fail Senator Paschal Mooney, a fervent opponent of fracking, expressed concern that this latest role could render the research unacceptable.
He said: "Quite frankly this survey, as it is currently being operated is so deeply flawed in the minds of those who are watching and monitoring the development of the process of hydraulic fracturing in Ireland, to the point where I don't believe that they will accept the conclusions of this report simply because CDM Smith are directly involved."
He later added: "This report isn't asking fundamental questions of whether Ireland should extract fracking gas but rather it is concerned about how to frack. In other words, the whole process screams with the view that this survey, being led by a pro-fracking company, is going to conclude that it is justifiable to introduce fracking into this country so long as the regulations are complied with."
Richard Boyd Barrett, from People Before Profit, said there was a "hopeless conflict of interest" by using CDM Smith.
He said: "The whole exercise has been compromised from the word go."
As a regulator, the EPA is obliged to look at controversial and topical issues, the committee was told.
"Because we are charged with protecting the environment we also look at issues coming down the tracks," said Mr Lynott. "When we started seeing fracking on our horizon, as an agency we needed on behalf of the Irish people, to find out more about it.
Meanwhile, Sinn Fein TD Michael Colreavy said there was virtually no political support for fracking.
He said: "We are doing a detailed, expensive study. We have a population who is exceedingly concerned about their agri-tourism, agri-food, their fishing, that their water is going to be poisoned and the place in which they live and love will be turned into an industrial wasteland.
"My concern is that this whole project seems to have taken on a momentum of its own. There is a train heading towards fracking and I don't know who the driver is."