Two senior officers have left Brisbane City Council over a $60 million blowout for technology upgrades, as Mayor Graham Quirk tries to get the project back on track.

Cr Quirk revealed in January that council's $122 million project with TechnologyOne to merge 13 systems into one by mid-2017 would be delayed by 18 months and cost about 50 per cent more than originally slated.

"Two senior players have gone," Cr Quirk told ABC Radio Brisbane.

"They made the decision after discussions with the CEO. There has been an agreement across the board.

"I don't believe there will be anymore [people leaving] at this time."

Council is trying to renegotiate its contract with the Brisbane-based TechnologyOne, including a six-month deadline for an acceptable system to be delivered.

It would also see the appointment of a systems integrator to help with implementation.

"This is a work in progress ... what we are trying to do with the vendor now is renegotiate the contact to get it back on track," Cr Quirk said.

"We are pulling out all stops to do that.

"We have to look after the interests of ratepayers."

TechnologyOne defends work on project

TechnologyOne told the ABC it was continuing to work with the council to deliver a successful project.

Its spokesperson said the company's contract banned it from making direct comments to the media, however it pointed to two previous statements issued to the ASX.

TechnologyOne boss Adrian Di Marco has blamed the council for contract changes. ( Supplied: TechnologyOne )

They said the council substantially increased the scope of the project after it started, doubling the "business processes" than what was originally contracted for.

"The delays are due to well-documented changes in project strategy requested by the BCC," TechnologyOne chief executive Adrian Di Marco said in one of the statements.

"In the worst-case scenario of litigation, given the fact above, TechnologyOne remains confident of its legal and commercial position."

TechnologyOne said its contract with council was worth $50 million over a decade for the cost of development, configuration, implementation, interfaces and data migration.

The remaining $72 million of the original contract were costs associated with council staff and contractors.