A Co Tyrone-based building firm at the centre of a school safety controversy is suing the Republic's Department of Education for more than €750,000 (£647,000) in overdue payments.
Western Building Systems (WBS) has initiated legal action in Dublin's Commercial Court seeking the final payments due on eight school building projects.
WBS confirmed it had initiated proceedings recently, but would not comment any further.
It is understood that the company is seeking what is known as retention money, a feature of construction contacts that allows for the withholding of a final payment as security for satisfactory performance.
It is the latest development in a major dispute between the department and WBS over building and safety standards at a number of schools built by the company.
It emerged last month that Irish Education Minister Joe McHugh has initiated 19 legal actions in the Republic's Commercial Court, a division of the High Court, against WBS over alleged defects.
Last autumn the Department of Education ordered structural checks at 42 schools built by WBS.
Three of the schools closed or partially closed to allow for remediation works, 19 needed external precautionary measures but did not have to close, while 19 required no intervention.
The checks followed the discovery of "significant structural issues" at Ardgillan Community College, Balbriggan, Co Dublin, which forced the closure of a section of the school.
The structural concerns at Ardgillan came to light during remediation work, which followed a fire safety audit conducted over the previous year in 55 schools, including 30 built by WBS.
As a result of the audit, extensive remedial issues, such as inadequate fire protection around emergency escape routes, were identified in at least eight of the 55 schools.