Several complaints were upheld following the independent investigation by legal firm VWV that concluded in February, with its findings published ahead of a meeting on Monday.
The report described the legal basis against the complainants as “sound”, but concluded the authority’s action “was a result of the bunker mentality at the council at the time and the desire to ‘get the job done’.”
It also labelled the authority’s approach as “heavy-handed”.
It said the impact on the complainants “cannot be underestimated” and criticised the delay.
“The handling of the complaints means there are four residents who have been let down,” the report added.
“It will not be enough to simply apologise again.”
The council admitted the process had “taken longer than necessary, and an external investigator should have been commissioned earlier”.
As well as calling for “full and complete apologies”, the report’s other recommendations related to governance, how the council’s legal team works, and the authority’s culture.
Officers have advised councillors to accept its findings in full and endorse an action plan when they meet on Monday.
A previous independent review of the council’s behaviour during dispute, known as the the Lowcock Inquiry, said there had been a “failure of strategic leadership”.
In response, the authority acknowledged its “poor” behaviour towards campaigners and residents and issued personal apologies to some individuals.