The public broadcaster argued that wardrobe purchasing was exempt from freedom of information legislation because it is “programme-related” information.

However, the information commissioner this week rejected RTÉ’s arguments and directed the broadcaster to release the information.

RTÉ’s decision was challenged by journalist and transparency campaigner Ken Foxe of Right to Know CLG.

The broadcaster sought to rely on the BBC’s clear “programme-making exemption” — covering all information held for the purposes of “journalism, art or literature” — under the UK’s FOI regime, which it contended was similar to the Irish legislation.

In his decision, senior investigator Stephen Rafferty highlighted the “non-binding nature of judgments from other common law jurisdictions” and said it was obliged to “interpret the 2000 Regulations based on the language contained therein”.

He rejected the argument that “records of financial transactions in respect of wardrobe” were related to editorial processes.

He also rejected RTÉ’s claim that some of the information was personal as it could identify individual members of staff for whom clothing was bought.

Mr Rafferty concluded: “Having carried out a review under section 22(2) of the FOI Act, I hereby annul RTÉ’s decision.

“I find that it was not justified in withholding certain information relating to the purchase of items for the costume/wardrobe department for a specified period by virtue of the Freedom of Information Act, 1997 (Prescribed Bodies) (No. 2) Regulations, 2000 or on the ground that some of the information is exempt under section 37(1) of the Act.

“I direct RTÉ to release the records at issue in full.”

RTÉ has four weeks to decide whether to appeal to the High Court.