The mistake, discovered by an external audit by Ernst & Young, occurred in June, meaning the council has been working from an incorrect budget for the last six months.
Publication of the council's budget was postponed from December when the mistake was discovered. E&Y were called in for an emergency probe over Christmas and are still working to identify the exact cause.
Leader of the Lib-Dem council Tim Bick told the BBC that a council tax rise was unlikely but could not guarantee that services would be protected.
"These errors change nothing in the council's actual resources. But for a period of three months the forecasts allowed the council to take a more positive view of the future than was the case in reality,” said Bick.
Opposition Labour group leader Lewis Herbert called for an investigation, saying, "No one finds £2.3m slipping through without major system problems.”
Cambridge council has said that revised budget proposals will be published "very shortly".