A "collective failure of leadership" at a council led to a £29m deficit in its finances, a report has found.
It said the leadership did not realise the scope of the problems or act quickly, and there was a failed programme of savings.
Bristol City Council is also criticised for not accepting the need for "challenging cuts" or hearing bad news.
Former elected mayor George Ferguson accused the current administration of spending money on "blame games".
The former cabinet member for finance, Geoff Gollop, said he never knowingly provided "incorrect information".
"As a cabinet member you work with officers, but you rely on the information that they provide you with," he said.
Former chief executive Nicola Yates has been unavailable for comment.
Mr Ferguson issued a statement saying: "I only heard about this review yesterday afternoon - which says it all - this administration is more interested in spending our money on reviews and blame games."
Bristol City Council later clarified Mr Bundred's review "was provided at no cost" to the authority and paid for via "an external grant".
Following the mayoral elections in May 2016 the authority asked consultant Steve Bundred to undertake an independent review of the causes.
He accepted while some financial problems were not of the council's making it did not deal with the issues early enough.
Mr Bundred, a former chief executive of the Audit Commission, said there had been a collective failure of leadership in achieving past savings and how the council managed the process.
But he acknowledged the council had "taken steps to put things right", with "regular and stronger financial reporting".
Elected Mayor Marvin Rees promised to keep a "very firm grip" on finances.
"The report suggests that in the past the political leadership was too complacent in trusting that savings could be made without making really hard choices," he said.
The union Unison said the mayor was... "right to take a hard look at poor leadership and culture among senior management.
"Now is the time to change that, and we want to work with Marvin to ensure frontline staff can get on with the job."