The attorney general, George Brandis, has lost a landmark freedom of information case against the shadow attorney general, Mark Dreyfus, and must continue to process a request for access to his diary records.

The case began more than two years ago when Dreyfus sought access under freedom of information laws to diary entries that showed Brandis’s government-related appointments.

But Brandis knocked it back on the grounds it would substantially and unreasonably interfere with the resources of his office, arguing in part that some of his diaries were national security matters which required substantially more detailed consideration. Dreyfus appealed to the administrative appeals tribunal and won.

In a surprise move, Brandis appealed against the ruling.

The full bench of the federal court dismissed Brandis’s appeal and ordered him to pay Dreyfus’s costs.

Outside court Dreyfus said Brandis’s “stonewalling attitude” may have cost taxpayers more than $50,000. He called on Brandis to rule out going to the high court to appeal against the decision.

“I welcome this decision today,” Dreyfus said. “It’s a victory for transparency and accountability.

“As late as this morning, Senator Brandis was claiming this was an important matter of principle. It raised no point of principle. It raised no point of scope.”

Australian government agencies commonly use the section Brandis relied on to refuse to process freedom of information requests on the basis they would unreasonably interfere or burden their resources.

They regularly claim, as Brandis did, that they need to consult a wide range of third parties.

The Dreyfus decision now sets a high bar for agencies that wish to rely on this section to refuse to process FoI requests. The full bench of the federal court relied heavily on and cited with approval the reasoning of the tribunal decision made by Jagot. They viewed favourably Jagot’s assessment that there was “no rational basis” that would lead to the conclusion that such a large number of parties named in the diary entries would need to be consulted.

Dreyfus also took the opportunity to urge the attorney general to appoint a new freedom of information commissioner and information commissioner. The positions have remained empty for 18 months, after the government’s failed attempts to abolish the office.