The Comptroller & Auditor General, Mr John Purcell, has questioned official projections for cost savings arising from the use of the proposed electronic voting system.
At a meeting of the Dáil Committee of Public Accounts, Mr Purcell also maintained that the Department of Environment, Heritage and Local Government had been lulled into a false sense of security after two pilot tests of the system.
He said the limited scope of the testing carried out on the system proved to be its "Achilles heel", although he accepted that the tight timeframe required for the system's development precluded the possibility of an "extensive dress rehearsal".
"I did make the comment in correspondence with the committee about the need to be absolutely fastidious and to go for overkill in terms of testing," he said.
He was speaking after the head of the Department, Mr Niall Callan, told the committee that his Department had projected savings of some €13 million over 20 years on the basis of a "conservative" estimation that there would be 12 elections in that period.
After the former minister, Mr Michael Smith, led questions for the committee, Mr Purcell said there was a "big 'if'" surrounding the possibility that the system itself could be used for 20 years.
Later, Mr Purcell said there was "a very large 'if' " surrounding the cost-saving projections developed on the assumption that the system would be used for 20 years.
Stating that technology was likely to advance significantly in that period, he said the Department's cost-benefit analysis was not as rigorously done as it should have been.
"I think there's a large question mark about the cost savings, the cost benefit, that was set out," Mr Purcell said.
He said the Department did not appear to have rigorously pursued the question of avoiding some €680,000 in costs when 400 voting machines used in the Nice Referendum were bought before modifications already required were made.
Mr Callan said earlier the "precise extent of cost savings" would only be determined through extended use of the system.
He made the point that the same number of staff would be required to staff polling booths, but added that 1,200 fewer workers would be needed to count votes.
In a separate development, the committee chairman, Mr Noonan, defended his right to criticise the electronic voting initiative before yesterday's meeting.
Responding to Fianna Fáil TD Mr Seán Fleming - who cited his comments in The Irish Times yesterday - Mr Noonan said he was entitled to comment as a TD on the basis of the first report of the Commission on Electronic Voting, which was in the public domain.
He said he took care not to comment in the paper on Mr Purcell's report, which was under discussion yesterday at the committee.
