In fact, it is not only from the act. I believe it is as well from government policies, but also from court decisions where fees have been challenged and the court has indicated that there has to be a reasonable relationship between the costs incurred and the fee. If not, if the fee is much higher than the costs, it can then be deemed a tax, and only Parliament can impose a tax.
On May 8th, 2008. See this statement in context.