The Cork brothers claim commissioner Helen Dixon has failed to properly deal with and finalise their complaint of November 2014.
Michael Cush, for the brothers, has secured leave to bring judicial review proceedings against the commissioner.
It was made on an ex parte basis, with one side only represented before Ms Justice Mary Faherty. The case will come back before the courts in May.
The brothers want orders compelling the commissioner to discharge her statutory duty in relation to their complaint.
They claim the alleged failure to finalise their complaint in a timely fashion breaches their rights under the European Convention on Human Rights and Charter of Fundamental Rights of the EU.
After the O’Flynn group loans were transferred in early 2010 to a Nama company, National Assets Loan Management Ltd (NALM), the brothers say the group engaged with Nama about restructuring their loans with the intention of continuing in business.
To that end, they gave Nama documents comprising at least 2,000 pages, including “highly confidential and personal” information about their business and personal affairs, they claim.
Nama sold their loans in May 2013 to Carbon Finance Ltd for a reported €1.1bn.
In September 2014, they asked Nama’s data protection officer for any personal data kept by it concerning them which, under the Data Protection Act, should have been supplied to them and within a maximum 40 days, they claim.
Nama provided them with certain limited personal data, they claim.
It is alleged the Nama response failed to meet their entitlements under the Act and they made a complaint to that effect to the commissioner in November 2014.
Michael O’Flynn wrote to the commissioner in June 2015 about the delay, saying the information would be relevant to evidence he was asked to provide for the Oireachtas banking inquiry.
In correspondence, the commissioner had stated that documents were being sought and any delay finalising the complaint was not surprising given the very substantial documents identified by the brothers as potentially containing their personal data.
In January 2016, the commissioner said an investigation would proceed without delay and various updates were provided over the coming months.
On March 6 last, having received no findings or final decision, their solicitors told the commissioner proceedings would be taken.
In separate proceedings yet to be heard, the brothers and their company, O’Flynn Construction, allege Nama and NALM leaked “confidential” information concerning them and that undermined the marketing strategy Nama had agreed with them.
That case is also against Enda Farrell, a former employee of Nama, with an address in Belgium.