Fine Gael claims it has evidence of political interference by the Taoiseach in the choice of the Mater site on the north side of Dublin as the location for the national children's hospital.
Fine Gael senator Brian Hayes last night released the text of a letter written by the Taoiseach to the then minister for health, Micheál Martin, in 2002 in which Mr Ahern referred to the Mater site.
In the course of the letter about the level of services being provided at Temple Street hospital, Mr Ahern wrote: "Given that the intention is to move Temple Street on to the Mater campus and to provide a state-of-the- art children's hospital for north Dublin, and indeed the country, any further downgrading of Temple Street would not be in anybody's interest."
Mr Hayes maintained that the letter shows that the Taoiseach was pressing his minister for health in relation to the allocation and distribution of paediatric services in the Dublin area at the time on the assumption that the new national children's hospital would be sited at the Mater.
"This new piece of information suggests that the fears of political interference in relation to the selection process for the new national children's hospital were grounded in reality," Mr Hayes said.
"In light of this revelation it is absolutely imperative that the call made by the Fine Gael leader Enda Kenny that a full independent review take place in respect of the selection process be adopted immediately."
Mr Hayes said the decision affect the lives of hundreds of thousands of parents and their children over the next 50 years.
"We must not take the wrong option now, informed by a process that lacks transparency and potentially driven by narrow political interests. Our children deserve better than that."
Mr Hayes is a Dáil candidate for Dublin South West.
Earlier, the Fine Gael leader expressed "deep suspicion" about the way the controversial decision to locate the children's hospital at the Mater site was made. Mr Kenny called on the Government to begin an immediate review of the process surrounding the selection of the site before any further action was taken.
"I am seriously concerned that two hospitals, Tallaght and Crumlin, have both withdrawn from this process," Mr Kenny said. "The fact that those decisions were taken and given the credibility of the personnel involved, has led me to having a deep suspicion that something is amiss with the process as conducted."
Mr Kenny said he was also concerned that the sites considered during the process were not rated under the nine McKinsey criteria which were the basic terms of reference in the evaluation of submissions, neither was there sufficient clarity and transparency about the process used to support the selection decision.