Three councillors voted against the motion: Simon Nixon, Malcolm Dixon and ultimately unsuccessful mayoral candidate Damon Harvey.
In October 2019, investigator Alastair Hall was instructed by Hastings District Council chief executive Nigel Bickle to carry out the review.
Hall was tasked with determining if there was an improper disclosure of information on two separate occasions, and, if so, the source of the leak.
The search for the leak entailed checking councillors' iPads, council's email server, InfoCouncil, HPRM, the Hub and councillors were asked to sign affidavits saying, in essence, they were not the source of the leak.
Two chose not to - Simon Nixon and Malcolm Dixon.
Both were interviewed by Hall, who said in his report that they had both explained their reasons for not signing it, and were "clear and forthright" that they had not leaked the agenda or information relating to it.
The pair also expressed their concern and disappointment that it had been leaked.
Hall was also tasked with providing recommendations on improving internal systems and processes relating to confidential information including 'public excluded' agenda items and council meetings.
The report concluded there had been an improper disclosure of a public-excluded agenda item or information related to it, and a 'strong inference' one or more councillors, directly or indirectly, had improperly disclosed information from councillor-only meetings.
The investigation was unable to identify the source for either action.
Bickle said the report noted hard copies of council agendas could be shared without leaving a digital footprint.
"While this review was unable to be conclusive in relation to the source of the leak, it has resulted in a set of recommendations for improving council's processes around access to confidential information," Bickle said.
"The report made recommendations relating to policy, process and technology, some of which have already been implemented. We will continue to work through the recommendations to minimise the risk of improper disclosures in the future."
View the full report below