The council employed experts to help design new roads like the proposed M28, the Cork-Ringaskiddy road, and paid them €2.12m.
The next biggest payout, of €866,679, was spent on external legal services.
A total of €604,000 was given to consultants working on environmental service projects, while a further €259,410 was given to those brought in to help with water service projects.
Consultants were also brought in to help the council’s economic development and tourism unit, being paid €72,660.
Cllr Des O’Grady (SF), who had sought a report on the fees paid out in 2015, was highly critical of the use of external experts, saying he believed the council had very professional in-house staff who could do these jobs.
“The council appears to have become overdependent on outside consultants for routine tasks,” said Mr O’Grady.
He said the council also employed a “large consultancy firm” to make a submission to Minister Simon Coveney’s housing activation fund.
Cllr Melissa Mullane (SF) agreed with him and asked if any cost-efficiency analysis had been done on outsourcing.
Cllr Eoghan Jeffers (SF) expressed concern about the amount of money given to consultants for road design and maintained that council staff could have done the work.
Other councillors took an opposite view. “If we didn’t have consultants we would be waiting years to get anything done. We don’t have enough staff. In the last eight or nine years we have been drained of staff [because of a recruitment embargo],” said Cllr Kevin Murphy (FG).
Cllr Frank O’Flynn (FF) said last year the council had invested €83.9m in capital (building) programmes so the amount of money spent on employing consultants to help such projects alone was miniscule.
He also pointed out that the report showed €2.9m of the amount spent on external consultants had been recouped from various bodies such as the Office of Public Works, Transport Infrastructure Ireland, and the Department of Housing.
“I presume most of these [consultancy] companies are based in Cork, so we’re helping local employment. It would be better if we could have in-house expertise, but that’s not been possible in recent years,” said Cllr Joe Harris (Ind).
Council chief executive Tim Lucey defended the outsourcing because “the county would grind to a standstill if we didn’t employ consultants”.
He said there were significant costs in defending legal actions against the council.
“We can’t defend serious cases unless we have the right personnel.”
Mr Lucey said the pick-up in the economy was likely to lead to an increase in government spending which would add to the amount of investment in the coming years in local authority-run projects. He said this would probably in turn require the council to employ more external consultants.