Swansea Council will give its IT staff just two weeks' notice of their new terms and conditions of employment before they are transferred to Capgemini.
Last summer the council's IT staff went on strike for two months after they discovered that their jobs were to be outsourced.
Of the 90-strong IT department at Swansea, 73 employees already know that they will transfer to the supplier on 1 October. However, Capgemini said the earliest date when the contract could be signed was 14 September.
The council has agreed to show the clauses that cover pay, pensions, new joiners and compulsory redundancies to Unison, the union representing IT staff, before it signs the contract. Capgemini has promised that the future pay rises of transferred staff will be protected.
Unison regional officer Jeff Baker said, "We have had a commitment from Capgemini in writing, but it says 'subject to the terms and conditions agreed with the council'."
Rory Murphy, director of HR sourcing at outsourcing consultancy Morgan Chambers, said, "It seems to be an illustration of dealing with the staff issues last, and that is just not the right way to do it. Is it any wonder that they have problems when they treat people that way?"
Swansea Council did not respond to Computer Weekly's request for confirmation that the contract would be signed only two weeks before the transfer of staff and declined to make any further comment.