The Ballarat City Council gave the go-ahead to the move at an ordinary meeting last night, despite only having approved the original design for the $4.5 million addition to the centre in October last year.

The spa had been part of draft designs considered last year, but was left out of the final proposal so the project could meet its budget.

But the spa was planned as a future addition to the centre and infrastructure such as pipes to allow its construction had been put in.

The urgency of last night's vote was due to the program of construction works at the site requiring a decision on the spa option.

The new works will be paid for by $253,739 from council asset sales and $185,229 from its cash reserves.

The new spa is to have disabled access and would replace a smaller existing spa that did not have disabled facilities.

Debate over the issue carried on for almost an hour before the motion was approved by six votes to two.

Councillors Des Hudson, Craig Fletcher, Mark Harris, Cheryl Bromfield, Ben Taylor and John Philips voted in favour of the move.

Mayor Judy Verlin and Cr Noel Perry voted against, while Cr Samantha McIntosh was out of the chamber to due a declared interest in the vote.

Some councillors argued that not to do the spa would leave the redeveloped centre incomplete, and the job would be more expensive in future.

"No one likes a smile with a tooth missing. To me that's what this would represent,'' said Cr Fletcher.

Cr Harris, who backed the plan, said the process for the redevelopment design had been flawed and was untidy.

Cr Verlin said she was convinced nothing had changed since October to justify the additional spending from the council.

"We're talking about a $450,000 upgrade. That's not something to be taken lightly."