Heard the one about the consultant? Someone who comes in and tells you what you do for a living then charges £1,000 a day for the privilege? Those who cannot do, consult? We could go on.

It's easy to be dismissive or cynical about a job whose definition is so fluid - an IT consultant has little in common with a PR consultant, for example, and neither would claim to be qualified as a management consultant.

The cynicism tends to go away when you see some of the impressive results they can produce, but things don't always go so well, and some of the consultants themselves have started making noises about the money being wasted.

Alastair Clifford-Jones, chief executive of management consultancy Leadent, has identified what he calls "consultancy addiction", the process by which clients get so hung up on having consultants around that they won't let them go.

"You just see that people are using consultants and work alongside them. You go to a meeting and next to them is a consultant. It's like losing the ability to make a decision." It wasn't just one client doing this either. "I think it's about how you treat your client. You create a dependency."

It's odd to hear this from someone whose business is pretty obviously in providing just the sort of service he appears to be running down, but he believes acknowledging this sort of addiction is in everybody's best interests.

"Clearly we're a business and not a charity. We're in it to make money. If we tell people we think they can do something by themselves then they acknowledge that we've helped train them to do so, and there will still be other projects in which we can take part."

There are cases in which the client offers too much responsibility to the external people, he believes. "We had an instance recently in which we started off by taking all the decisions.

"It was IT-led and it was all 'this bit of kit doesn't work, what would you do', and then gradually we found out by giving them confidence that they were able to take loads of decisions, so we were able to pull out."

Simon Rawling, head of project management consultancy PIPC, puts a lot of the onus on the client's stated requirements. "The consultant should help with the business and not run it," he says. "They can put a new IT platform in, put a required change in, but not run the day-to-day business.

"Many organisations we know tend to use consultants in lieu of staff when they have headcount freezes, for example."

He confirms he's seen consultants outstay their welcome in some organisations. "They charge by the day and I've seen consultants plant themselves and embed themselves until the client feels they can't live without them." His company's answer is to continue to demonstrate value and, above all, agree an objective and exit point in advance.

There are a number of strategies consultants can take to avoid getting clients "hooked", believes Clifford-Jones. "We would work with them in very much a coaching way; for example, if they were presenting a business case internally we'd make sure it's they who end up presenting, not Leadent." Often people ask consultants in to build their credibility after a decision has already been made - and that's when they ask the consultant to do the presentation, so that it looks independent. "But then they're owning the presentation," says Clifford-Jones. "We also tend to rotate people, putting different people in at different points of a project because people need different skills at different times."

There is a valid place for consultants, though. Much of the problem centres around communication and the powerbase that information can offer. Professor Eddie Obeng is learning director at the Pentacle Virtual Business School. "Consultancies leave a culture of dependence because there is no knowledge transfer between themselves and the client in the implementation of a programme. They solve the problem at hand, but they don't leave any theory or tools in the hands of their clients.

"In order to succeed in the long-term, businesses need to be led to implement the tasks for themselves - not for somebody to chase the tasks directly."

He adds that often there is a sense of failure because of escalating costs. "Businesses have long been using the adjective 'strategic' as a proxy for 'loss making', a malady that has been exacerbated by the rise of expensive strategy consultants."

Consultancy isn't a bad thing, and it's probably healthy that the practitioners themselves are leading the charge against its more exploitative excesses. The thing to remember is that consultancy for its own sake, like anything in business, is unlikely to deliver a positive result.

The smaller organisation can be particularly vulnerable to the brow-beating, "you need us to make this change" approach, but there can be good reasons for appointing a specialist.

n It might not be economic to hire a full-time PR/technical wizard/other non-core specialist to the staff;

n The owner or manager may be able to make a change or decision by themselves, but his or her time may be better spent on a core task;

n Your need might be short-term, so you just don't need anyone who's going to hang around any longer than necessary.

Whether any of this puts you at risk of dependency is open to conjecture and will depend on the sort of consultant you've hired - and, frankly, whether they have any scruples or not.

The thing to bear in mind is that although Leadent and others believe themselves to be proactive in weaning clients away from them when they're no longer needed, that's not the view taken by everyone. And inevitably it's the bad ones who won't tell you when you don't need them.