Canberra could lose the Immigration Department and Australian Border Force to another city if the "infighting" over the sought-after lease continues, the Canberra Airport has warned.

Airport chief executive Stephen Byron says "fallacies" about the potential ruin of Belconnen are being peddled by vested interests determined to keep the government department in the northern town centre.

Mr Byron, who is pitching strongly to bring the newly merged Immigration and Customs operation under one roof at Brindabella Business Park next to the airport, says Canberra developers must realise they are now competing with other Australian cities for valuable Commonwealth department leases.

Responding to warnings of "severe social and economic consequences" for Belconnen if it lost the 4100 Immigration workers based there, the airport chief said they were "spurious assertions" from vested interests determined to stop the department leaving its present location.

Several developers around town are vying for the signature of the department which wants to bring its 5500 Canberra-based public servants, currently scattered between Belconnen and Civic, together under one roof

Canberra Airport has drawn up plans for a 74,000-square-metre building at its Brindabella Business Park, which it says would be perfect for the department. Mr Byron says 2000 construction jobs would be created on the $385 million project.

But he said the tender should go to the builder that offers the best offices at the best prices to a government that has already demonstrated its willingness to take public servants out of the capital and is desperate to save money.

"We are not competing so much against each other as we are really competing against the rest of Australia," he said.

"The rest of Australia is well and truly in the game: the Tax Office to Gosford, the Australian Bureau of Statistics to Melbourne, Agriculture to the regions."

"If [Canberra] landlords win through higher prices as opposed to market solutions, then that costs jobs.

"You have to ask what is best for the Australian Border Force and what is best for Canberra.

"They are a part of the Australian government that we want to retain in Canberra for the long term."

Mr Byron said he was worried about the infighting between different parts of town that had developed over the prospect of Immigration moving to the airport.

"What I'm concerned about is that there is no other city in Australia that would be infighting about moving 4000 staff in a company across town to a new project that would deliver 2000 jobs ... and would cement its presence in this town forever," he said.

"That's true whether they go to airport or whether they go to the city or Woden.

"But there's a certain lack of credibility, a certain lack of substance when then best argument for the tender for Belconnen is that they must not be permitted to leave Belconnen.

"That is based on the very inaccurate and very spurious assertion that the very viability of Belconnen as a town centre is at risk."

Mr Byron pointed to the sale in Belconnen this month of Canberra's largest ever apartment development site for a record price of $22.1 million as evidence that the predictions of ruin for the precinct were "baloney".

"The winning bidder, like all the other bidders, has a realistic and confident view of the future growth of the Belconnen town centre, whether Immigration stay there or not," he said.

"The Belconnen town centre will continue to thrive, despite these spurious assertions ... it is being boosted by 300 apartments that will be finished next year, boosted by the growth of the University of Canberra and associated construction and development, boosted by 340 apartments on the Westfield site."