UNION officials expect public servants based in Brisbane's CBD will be forced to move to Icon Ipswich as the opening date edges closer.
Icon Ipswich is expected to be occupied by 1200 public servants in seven months time, but who they will be is yet to be decided.
Together Union secretary Alex Scott expressed concern that workers living on Brisbane's bayside would be forced to travel hours to Ipswich each day.
The Public Service Commission said 450 public servants based in Ipswich had already been allocated to Icon Ipswich and expected the remaining 750 to be shifted from Brisbane.
"The Public Service Commission is still liaising with a number of government agencies about Brisbane-based work units who will relocate," a spokesman said.
"This should be finalised by the end of April."
But Together Union secretary Alex Scott was sceptical the April deadline would be met.
Mr Scott said Ipswich was home to thousands of public servants who travelled on the Ipswich motorway and train line to work.
Mr Scott said the task of identifying the workers had begun.
He said Ipswich was not the problem, but the extra hours of commuting acted as a deterrent.
"People that live in Redcliffe and Wynnum are desperate not to go, but people living in Ipswich would love to," he said.
"Clearly it's going to put more stress in the workplace. Workers, whether they are in the public or private sector, generally put in extra hours.
"But if you are travelling for hours to get to work, they are less able to put in the extra hours.
"They can smash through with it, but it will become a more toxic and less productive workplace," he said.
Construction of the nine-storey tower is progressing on schedule with the State Government to begin its 15-year lease on the building on October 1.
Mayor Paul Pisasale has offered to give potential Icon Ipswich workers a tour of the city in a bid to attract more of them.
The shifting of public servants became a sticking point when the LNP won last year's election.
The premier said public servants did not want to move to Ipswich.