Porirua's loss will be Wellington's gain when the New Zealand Defence Force moves this year.
About 150 communication and information systems staff would relocate from Porirua to Wellington later this year, a defence spokesman told The Wellingtonian.
The move will cost Porirua 150 jobs.
The Defence Force is currently at the Cityfitness gym building, 1 Walton Leigh Ave.
"The Porirua lease is expiring and Defence is taking the opportunity to consolidate its Wellington staff, and make better use of its existing buildings," the spokesman said.
"Nobody is losing their job as a result, and Porirua staff have been aware of this move for two years."
A scathing report on Defence Force cost-cutting was released last week by Auditor-General Lyn Provost.
The move was criticised by Mana MP Kris Faafoi and Porirua mayor Nick Leggett.
"The Defence Force has had a presence in Porirua for 30 years in a building well equipped for its needs," Mr Faafoi said.
"News of the departure certainly feels like an assault on Porirua."
He doubted the department would save money by leaving a low-rent building, especially considering the move would likely incur millions of dollars in relocation costs.
Mr Leggett said many businesses were moving into Porirua because of its low commercial rents and good regional location.
"The Government seems to be going in the other direction."
- The Wellingtonian