The news comes as front-bench solidarity on the controversial plan looks increasingly shaky with Treasurer Scott Morrison failing to back the certainty of colleague Barnaby Joyce that the move was a done deal in the event of a Coalition victory on July 2.

Mr Joyce announced on Thursday that Australian Pesticides and Veterinary Medicines Authority was going to move to Armidale in Mr Joyce's electorate of New England and the public servants who work at the agency better get used to the idea.

But a cost-benefit analysis of the move, ordered by Prime Minister Malcolm Turnbull in January, has still not been done despite being due for completion on Friday, the Financial Review has reported, the day after Mr Joyce's announcement.

Several groups in the farm sector, including Animal Medicines Australia, CropLife Australia and the National Farmers Federation, as well as federal Labor, the ACT Government and public service unions are against the plan. ACT Senator Zed Seselja has added his voice to the growing chorus of opposition.

Mr Morrison was less than whole-hearted on the weekend in his support of Mr Joyce's position that only a Coalition defeat on July 2 would derail the northern exodus.

When asked in a TV interview about Mr Joyce's approach, the Treasurer said: "No, we will work through the details to make sure this can be done effectively. That's how a team works together.

"Barnaby has a strong plan and advocacy for rural and regional Australia and we will work with him as part of that Coalition and that team to make sure we do it in the most efficient way possible."

Meanwhile, the Agriculture Department has insisted the cost-benefit analysis is still not ready and has tried to explain why it took more than three months to hire accounting giant Ernst and Young to get the work under way.

"The procurement process involved a number of steps," a spokeswoman said.

"The department undertook stakeholder consultation to inform the scope of work, and followed the Australian Government's Commonwealth Procurement Rules."

Mr Joyce's office said on Friday that more detail on the fate of the analysis would be forthcoming but it had not been provided by deadline on Monday.

Senator Seselja re-iterated his disappointment at the decision but said he was lobbying public service authorities to allow transfers for APVMA staff who did not want to go to Armidale.

"I have expressed my disappointment at Barnaby Joyce's decision to relocate the APVMA to Armidale," he said.

"I have written to the Public Service Commissioner to ensure that employees who do not wish to relocate are supported and their expertise is not lost to the Australian Government," the senator said.

"There are good reasons why most departments are based in Canberra and that's because we are home to a high level of public policy expertise.

"I will continue to fight to keep jobs in our Public Service Departments local."