The amount spent by the government in Northern Ireland on external consultants has more than doubled over the last five years.
The report said spending was not always well managed
According to a report published by the Public Accounts Committee, the cost of taking professional advice from the private sector totalled £42m in 2007.
Government departments hire consultants for advice on a range of subjects from finance to the environment.
The Stormont PAC report said this spending is not always well managed.
It also found that best practice guidelines are not always followed.
The report said civil servants were in danger of becoming dependant on consultants and do not appear to be building an efficient and well skilled civil service.
The PAC report said that private sector consultants are increasingly designing and managing public services.
The committee said that departments must ensure spending is justified.
Committee chairman John O'Dowd said: "Now that we have a stable executive and a PAC which is going to be reporting on a regular basis, things will have to change.
"We did welcome the fact that during the evidence session that the Department of Finance did say that this is one of the areas they want to closely examine and tighten the reins on."
The Institute of Business Consultants said it believed its members are delivering value for money, but pointed out that this is not always the same as the cheapest price for the job.