More than 100 ministerial decisions or announcements were made by Barnaby Joyce and Fiona Nash since October 2016, according to the parliamentary library, which Labor now claims could be challenged due to their ineligibility to sit in parliament.

The research, released by Labor on Monday, compiles a list of government decisions made or announced by the pair including relocating the Australian Pesticides and Veterinary Medicines Authority to Armidale, elements of the regional national broadband network rollout and the mobile blackspot program.

The research undermines attorney general George Brandis’s claim that there are “no legal consequences at all” to the high court finding Joyce and Nash are ineligible but may provide some support to his claim that most decisions are those of cabinet or the government, not the individual ministers.

Joyce has defended the fact he stayed in cabinet, arguing that his decisions are still valid because he was an MP until the high court ruled him ineligible.

Labor has obtained legal advice that Joyce and Nash may have contravened section 64 of the constitution by “purporting to hold office as a minister for more than three months” after the date they were sworn in. The advice suggests their decisions made after October 2016 could be challenged.

In that time Joyce held the agriculture and water resources portfolios and gained resources and northern Australia after Matt Canavan quit cabinet. Nash held the regional development, regional communities, local government and territories portfolios.

The advice argues the effect of such a contravention is retrospective, although it acknowledges there is “no authority directly on point”.

The parliamentary library identified 20 legislative instruments and 47 ministerial announcements made by Joyce and eight legislative instruments and 43 announcements made by Nash in the relevant period.

However, the research notes that only the legislative instruments were “explicitly made by each minister” and the extent to which they were directly responsible for approving funding for the announcements could not be confirmed in the time available.

In August Labor argued that the potential invalidity of their decisions provided further reason for Joyce and Nash to step down but the pair kept their portfolios pending the high court decision.

On Monday Joyce disputed the claim the high court’s ruling had a retrospective effect.

“You remain a member of parliament at the declaration of the polls,” he told Radio National. “You stay in until such time as … you die, you resign or you’re found ineligible by the high court, and at that point you’re therefore out of parliament, not before.”

On Sunday Brandis told Sky News he did not accept that the pair breached section 64 and their ministerial decisions were invalid but said “obviously we’re having a close look at that right at the moment”.

“I don’t think there are many decisions of Mr Joyce, as opposed to decisions of cabinet, that could be affected,” he said.

Brandis argued that most decisions were actually made by the cabinet on the recommendation of ministers and that appointments were made by the governor general.

“I think you’ll find there are no legal consequences here at all,” he said.

The parliamentary library suggested that decisions made by Joyce subject to challenge include the relocation of the APVMA, various grants and appointments, and decisions made under the Water Act such as determination of claims for payments for water access entitlements.

In the case of Nash it suggested that elements of the rural decentralisation program, NBN rollout, mobile blackspot program and grants under the Building Better Regions fund could be challenged.

Joyce said the decision to move the APVMA was a decision of cabinet that was ordered by the finance minister, so Labor’s argument was technically “flawed”.

Joyce accused Labor of wanting to reverse decisions that had benefited regional areas.

On Sunday the manager of opposition business, Tony Burke, told the ABC’s Insiders program that although Labor agreed with a series of Joyce’s decisions there would be “vested interests” who may have a reason to challenge them.

“If you’re in charge of Australia’s quarantine service, there’s importers or exporters who make or lose money depending on decisions you make,” he said.

“There’ll be a series of decisions there with vested interests, now combing through, and there being a whole lot of legal doubt over those decisions on the simple basis that Barnaby Joyce didn’t do what Matt Canavan did [and resign].”