Wagstaff said the industries were critical to the New Zealand economy and "we shouldn't be putting them at risk."
"We're in danger of repeating the experience of the 1990s when the loss of knowledge, expertise and adequate staffing levels in the public service led to disasters, and economic costs for the whole country,"
MAF director-general Wayne McNee said he expected the changes, which include plans to combine financial management, policy advice and communications, to realise savings of more than $18 million in the 2012 - 2013 financial year - higher than earlier estimates.
The proposal does not affect fishery officers, animal welfare officers and investigators, or quarantine inspectors and would be made without reducing front line services, he said.
MAF and the Ministry of Fisheries merged on July 1 and an interim structure has been in place since.
Wagstaff said staff were anxious about their jobs and were worried how the business will continue to function.
"We understand something like 700 jobs have been identified as affected from well over 2000 jobs, which means some staff may have to change their reporting lines."
State Services Minister Tony Ryall said earlier this year creating a single entity would reduce administrative duplication and costs.
- Susie Nordqvist