Half of the staff at the department Barnaby Joyce moved into his own electorate have left.

The Australian Pesticides and Veterinary Medicines Authority (APVMA) assesses agricultural and horticultural chemicals for use in Australia.

In 2016, former deputy prime minister Barnaby Joyce announced the APVMA would be relocated from Canberra to the rural NSW town of Armidale.

At the time, the authority had 198 staff.

At least 110 of its employees, including 33 regulatory scientists, have since departed.

“This has negative impacts in terms of the agriculture industry, in terms of the services the APVMA can provide, and that's problematic for everybody,” said public sector union spokesperson Brooke Muscat-Bentley.

A recent staff survey revealed just a quarter of staff are likely to move to Armidale.

The APVMA says it has filled nearly all of the vacancies, though many of the replacements reportedly do not intend to shift to Armidale.

The regulatory authority faces many other changes posed by the moved.

Construction of the APVMA’s new headquarters in the northern New South Wales town is weeks behind schedule.

Additionally, staff have rejected a $30,000 relocation offer as inadequate, saying they could still be left out of pocket.

Reports say there is also a high risk that customers will lose confidence in the APVMA, and will struggle to find suitable candidates for key roles.

“This has been a mess from the outset,” Ms Muscat-Bentley said.

“A decision has been made on a political whim to uproot all these people … this is something that should never happen again.”

The agency is now offering reimbursement of up to $55,000 for staff to relocate, and new retention bonuses worth thousands of dollars.