UP TO 100 people will lose their jobs after InterOil Corporation announced it will close its Cairns office.

The company recently confirmed it would relocate core functions from the office to support expanding operations in PNG.

All Cairns employees will either be made redundant or relocated to PNG or Singapore before office closure in the last quarter of the year.

One employee who provides the only income in his household said many staff would not be able to relocate internationally to keep their position if offered due to family commitments in Cairns, but some would also struggle to find another local job given their specific skills.

"A lot of these people have been with the company, riding its highs and lows, since day dot, and now they're being told they are no longer required," the employee said.

"They've turned a perfect office into a shell with this news everyone's just shattered."

The decision to increase capacity in PNG comes as InterOil this year finalises an agreement with French oil company Total S.A. to develop a multi-billion dollar liquefied natural gas project in the country.

InterOil spokesman John Hurst said "it was a clear business case" for the Cairns support office to be combined with the company's Singapore corporate office and InterOil was "still working through the mechanics" of exactly how many job losses there would be.

He said factors such as flight times, costs, access to markets and ability to attract resources were considered in the company's business review, with management deciding it was best to have "as many people in the company in PNG as possible" as InterOil transitions into the next phase of its development.

InterOil CEO Michael Hession said the move would "put resources where they are needed most", saying it "makes sense" to focus the company's workforce at its PNG base.

The Cairns Post understands the announcement was made to Cairns office staff a fortnight ago, with employees allegedly shown a slideshow detailing the company's future prospects in a positive light before being told changes included their office's closure.

Geologists, drilling specialists, IT support staff and finance department employees around 20-60 years old are among affected staff.

Another employee said it was implied during the announcement process that Cairns was regarded as "somewhat of a backwater" for an international mining company to reside.

But Advance Cairns CEO Mark Matthews said Cairns was well-established as a prime location for supply and service support to PNG mining companies.

"It's certainly an ideal region for this, so to hear of this loss is saddening," he said.