You should not, the argument goes, let them on site until you know what to do with them, particularly since in some markets consultants are so short of work there is a possibility that they might not tell you if they're really needed or not.
Here's the worst case: existing staff are too busy to deal with a project so a consultant is hired, but since decision-makers are also too busy to tell the consultant exactly what to do the project doesn't progress, the consultant leaves, much money is wasted and the project is further delayed.
Just as conventional wisdom says you should outsource non-core functions, consultants -- who generally have no long-term commitment or buy-in to your business -- should not be used for developing business strategy but rather executing it. Similarly, projects involving a high degree of innovation and risk should be done by insiders.
CIOs and IT managers here seem to broadly agree.
Garry Collings, information systems general manager of Tranz Rail, advises companies to clearly define what consultants are expected to do.
"That's where a lot of people go wrong," he says.
People tend to panic when they think there is no movement on a project, he says. They think getting consultants will fix that process, but this, unsurprisingly, does not always happen. And since a consultant's role is to leave once a task is completed, they cannot effectively deal with risk-taking options, he says.
Tranz Rail uses consultants for business analysis functions, that is, filling the gaps between business and IT and/or helping TranzRail turn business requirements into an IT project.
Collings says consultants make up "extra bums on seats", so that when they've completed their investigations TranzRail still owns the knowledge for the project.
New Zealand Defence Force CIO Ron Hooton argues that consultants won't necessarily be top guns so their duties should be narrowly delineated.
"Be very, very clear as to how you specify the outcome. Be absolutely certain about who is going to work on the project, what their skills are and their contribution to the project," he says.
"What we must get away from is the idea of consulting firms pitching a very senior person to do the work ... what often happens is they will get six inexperienced people working under the supervision of the experienced person," Hooton says.
The NZDF "very rarely" uses consultants nowadays, only employing them for "particular niche pieces of work we cannot do ourselves".
This has included a strategic study of the agency's engineering management system, a project Hooton says was successful in providing the right answers in terms of options.
Hooton credits the consultants for a job well done, but says had it failed the blame could have lain with the NZDF for not setting out clearly what was expected of the consultant.
The defence CIO agrees with those who argue that consultants should not define business strategy, saying this is the core of what a company does and its own internal staff should know this better than outsiders.
"I have seen examples of organisations that have used consultants to develop IT strategy and all they have left is an elegant book sitting on shelves. IT strategy works best if you and your team -- the people involved in the strategy -- come up with it themselves, because it has buy-in," he says.
However, Hooton agrees that if an organisation does not have the skills to carry out a task by itself, it should use outside help.
Insurance firm Royal Sun Alliance uses consultants to "facilitate the formulation of getting our business leaders to a focused decision", and occasionally for independent quality assessment.
"If you use them right, they can add much value to the organisation, but also create a lot of overhead. It is a matter of balance," says CIO Rob Flannagan.
Flannagan says scoping projects or assignments first is absolutely critical so that consultants know exactly what they are employed to do.
Victoria University uses consultants for project management and to provide resources when it does not have the staff to cope.
Information services director Cathy Budd says recent projects included creating a new infrastructure for servers and desktops. Vendors are also providing consultants and doing much of the work involved with a major upgrade of Victoria's student administration system.
The university generally claims success with its IT projects, but says any failures would lie with the university steering committee who employed and set out the terms of reference for the consultants.
"Bring in people who know what they are doing and have that experience elsewhere," Budd advises.