The Department of Education did not go through the normal procurement process when it engaged Canadian com- pany Polymetrika to implement and deliver the Leaving Cert calculated grades.
A department spokesperson said there was insufficient time to run the full process and instead it relied on an alternative, the Negotiated Procedure without Prior Publication, which "is used in circumstances where it is a case of extreme urgency".
Polymetrika developed the software for processing the data in order to come up with calculated grades.
Two errors in coding, for which it is responsible, have led to around 6,500 students receiving a lower grade than they should have.
Up to 1,000 extra college offers may now have to be made, and further checks are being carried out before the revised results are issued to ensure there are no more mistakes.
US-based consultants Educational Testing Service (ETS), which was commissioned by the Department of Education last week to carry out independent checks, may have its report back by today.
The department spokesperson said Polymetrika had recognised expertise in what is a highly technical and specialised field .
Its principal, Fernando Cartwright, is a former senior researcher at the Canadian Council for Learning and also worked with Statistics Canada.
Polymetrika was initially engaged on an advisory contract worth €75,000, but was subsequently given the task of implementing and delivering the calculated grades system, and costs have risen to €160,000.
"In order for the calculated grades model to be of value to students, results had to be issued by early September, to make Irish and international deadlines for entry to higher and further education," the department said.
"This imperative meant there was insufficient time in which to run a normal, full procurement process.
"The only way to achieve the goal of issuing calculated grades to students in the time available was to use an expert provider that is trusted, that had the skills and expertise to do the job and understood the Irish system."
In addition to Polymetrika, the Educational Research Centre carried out a number of checks, including a sample check of the coding used.
Meanwhile, Green Party leader Eamon Ryan told the Dáil yesterday that the Leaving Cert would go ahead next summer.
"The message to the upcoming Leaving Cert students is that there will be exams next May and June," he said.
Under pressure from Sinn Féin's Donnchadh Ó Laoghair about the week-long gap between the report of the first error and the public disclosure, Mr Ryan said there was no intention to keep anyone in the dark.
He said the Government has been assessing the scale and implications of the problem.
Mr Ryan said they would "make sure that there's no student who isn't able to avail of a course that they should have been able to access", adding that the problem had arisen from just "four characters being different in a 50,000-line code."
The CAO made a further 941 offers of college places for the current year to 868 applicants in yesterday's Round Three.
It includes 521 offers for Level 8 (honours degree) courses and 420 offers for Level 7/6 (ordinary degree/higher certificate) programmes. Some applicants received two offers.
The offers do not include any arising from the coding errors in the calculated grades process.
Once the revised results are released, on foot of the review from ETS, the CAO will make new offers as appropriate.