Daventry District Council has voted in favour of the unitary proposal with several members saying it was a 'sad day' for the district.
The scheme will effectively end the existence of DDC and the six other district and borough councils across the county, as well as the cash-strapped county council.
Daventry joined the county council, Northampton Borough Council, Wellingborough, East Northamptonshire, Kettering and South Northamptonshire in backing the reorganisation.
At the time of writing, Corby's council was still voting on whether to submit the proposal.
The current two-tier system of government, which has been in place since 1974, is almost certainly likely to be replaced by two one-tier unitary authorities, which would provide all services under one roof.
Daventry, Northampton and South Northamptonshire will become a West Northamptonshire unitary while Corby, Kettering, Wellingborough and East Northamptonshire make up a North Northamptonshire unitary.
"This is a sad day because Daventry District Council has been well run for years," said leader Chris Millar.
"We must try and influence and do our best efforts to not be neglected as the rural area and do the best for our residents.
Councillor Millar added that if Daventry did not accept the unitary plan then the district would lack influence in future discussions.
The proposal was backed by 22 councillors with seven voting against.