John Clayton, a former Audit Scotland chief, received the payment from Argyll and Bute Council.
The figures, revealed in a freedom of information request, showed he earned £29,121.88 over the course of the inquiry, which was completed in mid-May.
It is understood he billed for 60 days of work – which equated to a daily fee of £500 – during the investigation, which was launched after communications chief Jo Smith allegedly told a conference fake social media accounts had been used to monitor what was being said about the council.
With Ms Smith suspended on full pay for six months, the minimum cost of the inquiry is likely to be £50,000. The total cost, how-ever, will have to take account of the fall-out that saw press officers Janet West and Dinah MacKay resigning and short-term replacements brought in. Ms West and Ms MacKay left after it was claimed they misused the council's in-house internet system to share comments about senior members of the executive team.
The figures were given out just days after the council was criticised for snooping on nine-year-old Martha Payne's school dinner blog 1000 times before shutting it down, and then re-opening it.
The decision not to carry out the investigation internally, given the large fee, was criticised yesterday.
Eben Wilson, director of Taxpayer Scotland, said: "This appears to be an astonishing waste of taxpayers' money – on something that was surely unnecessary. Not only are there question marks about the appointment of Mr Clayton but an internal investigation could have been done at far less cost.
"Senior management need to answer some hard questions about why internal resources were not used. It appears as if they have lost control of their organisation. Local taxpayers should be rightfully angry at the fees that have been paid to sort out silly internal disputes. Council staff are paid to run services, not engage in a ferment of rumours and accusation.
"This issue should now be fully investigated by councillors, at low cost, and the senior management asked to answer for their apparent profligacy."
Councillors are now calling for an internal investigation into how Mr Clayton came to sign a contract with the authority. John McAlpine, of the Argyll First group of councillors, said: "My major concern with this is that in most circumstances we have to go through the tender process to appoint someone. What gave [chief executive] Sally Loudon – if it was her – the right to appoint someone of her own choice? Someone she had obviously known beforehand in a previous employment?
"If it was not her, then who was it and who authorised it?
"Even then, was this the best person to go to? We have our own HR department – could they have done it at a fraction of the cost?"
Independent local councillor Alistair MacDougall said: "I don't know who authorised this in the first place. That's something I will be digging into. It's a lot of money for nothing at the end of the day. I would have said this should have been an internal investigation with councillor involvement – that would also have got to the bottom of it."
Mr MacDougall questioned the wisdom of spending so much money on the investigation when there was reduced spend in the community on care packages and similar services.
It is understood Mr Clayton's report clears the press office of spying. Ms Smith is likely to face a lesser charge of bringing the council into disrepute for using the word "spy" in a presentation, when she appears at a disciplinary hearing next month.
The leader and deputy leader of both the administration and opposition were unavailable for comment.
An Argyll and Bute spokeswoman said: "In February 2012, Mr John Clayton was appointed to carry out an independent and exhaustive investigation into communications issues at Argyll and Bute Council.
"Detailed information about this decision was provided in a statement issued by the council on February 21, 2012.
"After an assessment process, the council's executive director of development and infrastructure services appointed Mr Clayton to provide the external resource required for an investigation of this nature.
"The report produced by Mr Clayton has not yet been released. Mr Clayton was paid £29,121.88 for his work over a period of more than 60 days."