Concern Wellington City Council's financial books aren't in a good state

Castalia was commissioned by a group of locals, for Independent analysis of public records, which suggests a one billion dollar budget blowout.

Group member and Wellington Lawyer, John Swan says the council's 'reckless.'

He says they've bitten off more than they can financially chew, but concedes some of it is down to inflation.

Council chief financial officer Andrea Reeves says the analysis makes assumptions based on outdated information.