All three of the investigations paid for in that time frame were overdue, according to the council’s protocol to resolve complaints within 12 weeks.
The cost was revealed through a Freedom of Information Act request submitted by the Local Democracy Reporting Service.
Three payments were made to legal firms since 2019 totalling £27,157.50 plus VAT.
Wilkin Chapman, the largest law firm in Lincolnshire and East Yorkshire, received two of the payments.
It was paid £3,309 between February 2019 and July 2019 to produce an investigation report following a complaint.
From February this year to date, it has been paid a further £8,130.50 for work on another investigation.
Bevan Brittan, a major law firm with offices across the country, was the other company paid to carry out an investigation in the past three years. From March 2021 to date, the council has paid it £15,718.
This relates to a complaint made by Marcus Combie, street tree campaigner, about the council’s use of legal privilege in emails and FOI. It was initially expected to be completed by May but is still ongoing and councillor Julie Grocutt, deputy leader of the council, said the final cost is expected to be in the region of £25,000.
It comes after Mr Combie found senior officials marking messages about the tree-felling programme as “not subject to FOI”.
In a council report, for a meeting of the audit and standards committee at the end of last month, officers said contracting legal companies to carry out such investigations allowed for independence and meant that appropriate resources were available to do the work.
They said: “This would appear to be a reasonable use of resource however their complexity still often requires a considerable period of time for the investigation to be completed.”
The report also showed there was a total of 63 complaints made about councillors, both at city and parish level, since 2019.
There were 22 complaints made in 2019, the following year there were 31 complaints lodged and so far this year there have been 10 complaints filed. Only the most complex cases lead to investigation by contracted legal firms.