Agencies requireing portfolio exclusion

So, I am having an issue with a client of mine. They are an agency, and it's the first one I have worked for before. They are very easy to work with and have never had any issues with them other than this.


So the problem is that they will not allow me to use any of the work I do for them on my own portfolio. The first time this happened was on their own company site, but we had a bit of a mix up over it and I let it slide for a nominal charge.

But I've recently gone in with them on a bid for anther site and got it. But again, they are telling me I cannot use it for my portfolio even though it was not brought up before hand. They are also telling me that they have never had another web designer say that this is a problem and that it is an understood rule that when you work for a large agency, you cannot use the work on your own portfolio. But a few of my old teachers say it's odd that they are not allowing me to do this.

So, what's the truth? Is it pretty normal for an agency to not allow you to use your work you do for them on your portfolio, and should it be charge for or not?

thank you!