The Ulster Unionists have called for a Stormont investigation into a Catholic school in Co Armagh after it was allowed to increase its admissions while a nearby state school was not.
Newry and Armagh MLA Danny Kennedy reacted with outrage earlier this year when Markethill High School's request to be able to take in more children was turned down.
He was further exasperated when St Paul's High in nearby Bessbrook was allowed to accept an extra 24 pupils in September.
Following an appeal tribunal, it has emerged St Paul's did not check addresses in seven cases.
The appeal was taken by a child earlier this month who had failed to secure a place at the school.
The tribunal was "not satisfied that the school had discharged its duty to verify addresses correctly and consequently had not applied its admissions criteria correctly".
Mr Kennedy said: "In June I raised my concerns at the difference in how Markethill High School was treated compared to St Paul's Bessbrook in terms of their respective applications for additional Year Eight places, known as temporary variation requests.
"The relevant section in the Department of Education turned both requests down, but in the case of St Paul's, the minister ordered the decision to be reversed, a decision hailed by Sinn Fein MP Mickey Brady as an example of 'team Sinn Fein delivering for people on the ground'.
"These concerns have been compounded by the findings of a tribunal on a Year Eight admission application for a prospective St Paul's pupil.
"The tribunal report details a litany of incorrectly applied admissions criteria at St Paul's. Even more alarmingly, it details that the school has not been discharging its legal duty to properly verify the correct addresses of applicants and therefore has not applied its admissions criteria accurately."
Mr Kennedy has called for Education Minister John O'Dowd to order an independent probe.
"I have little confidence that decisions surrounding admissions to St Paul's have been made on proper and purely educational grounds, and I will be raising my concerns at a forthcoming meeting with the chief executive of the Education Authority's southern region, Gregory Butler," he said.
"In addition, I am calling on the Minister of Education to authorise a fully independent investigation to look at whether St Paul's admissions have been manipulated over the past five years, and the circumstances surrounding the granting of the temporary variation by the minister in May 2015.
"To regain public confidence, we need full disclosure."
A spokesperson for the Department of Education said: "The minister is awaiting an initial report from officials on this matter. He is very concerned at the scale of the numbers involved as a result of the school not administering its admission criteria correctly.
"He will assess the report and take whatever action he believes appropriate to ensure the failings are corrected and not repeated."
St Paul's High School principal Jarlath Burns declined to comment.