"Especially once the losses of local democracy and the costs of change are taken into account."
TDB and consultancy Martin Jenkins compiled a different report in April, commissioned by Wairarapa councils. It also found Wairarapa could go it alone.
The report favours an "enhanced status quo".
It suggests combining key services, such as water and transport systems, is of greater benefit than combining the councils themselves.
For other activities such as environmental protection, recreation and sport, noise and dog control, the case for amalgamation was weak, it said.
The report said if there must be further amalgamation, it favoured having four unitary authorities - Hutt, Kapiti, Wairarapa and Wellington.
The impacts on rates would differ, depending on how the councils would be reshuffled.
The report estimates Wairarapa ratepayers would have a 26 per cent increase in rates under a single Wellington and Greater Wellington unitary authority.
Rates would increase by 13 per cent under a Wairarapa Unitary Authority.
Ultimately, the Local Government Commission would make the decision on the best option for Wellington local government.
Lower Hutt Mayor Ray Wallace says the report raises new options and important economic arguments that it will need to consider in its application to the commission.
The three district councils in Wairarapa and the Greater Wellington Regional Council have already applied.
The deadline is looming for alternative ideas for local government in Wairarapa and Wellington. It is August 16.
