Unions have accused Qantas of turning its back on Tasmanian workers by deciding to split its call centre businesses and boost staff numbers in New Zealand.

The Australian Services Union, which represents Qantas call centre employees and ground staff, say the company has backflipped on plans to send about 120 jobs to Hobart after closing its Melbourne and Brisbane centres.

Qantas said yesterday it would now hire about 70 extra full and part-time staff at its Hobart centre, following a decision to restrict calls taken at the site to "premium service" inquiries.

All other calls are to be taken in Auckland, where 50 new jobs will be created.

The ASU fears the decision could see the number of new Hobart jobs slashed to as few as 45.

In a letter to the union, Qantas said fewer employees than expected had chosen to relocate to Hobart from its Brisbane and Melbourne call centres.

It is understood of the company's 500-strong interstate call centre workers, just 11 applied to move to Tasmania.

ASU organiser Kath Ryman said the interest was not overwhelming, but there were more than enough local workers to make up any shortfall.

"Hundreds of Tasmanians have applied for 15 of the 45 jobs already advertised," Ms Ryman said.

"This decision significantly diminishes the chances of Tasmanian workers securing work with our national carrier."

The state government's $10.9 million deal with the company was premised on securing 246 existing jobs in the state and creating more opportunities for Tasmanians.

The sweetener included relocation assistance for interstate employees, an upgrade of the Hobart centre and payroll tax relief.

The state government said it had spoken with Qantas and was assured of the company's commitment to increasing job numbers at its Hobart site.

Denison Greens MHA Cassy O'Connor said the government must detail exactly how many jobs will be created through the multimillion-dollar deal.