The spending came during the period July 2008 to June 2009 after 41 transactions - more dealings than any other Championship club.
Spending on agents' fees fell by more than £2million across the whole of the Football League last year.
On announcing the latest figures, Football League chairman Lord Mawhinney said: "Given the current financial outlook, it is encouraging clubs are being more circumspect in terms of their payments to agents.
"In fact, clubs only committed to pay an agent 6% of the 3,700 player transactions that took place during the course of last season. This is the lowest figure recorded in the five seasons since publication of agents' fees began.
"I would like to think that in pioneering the publication of agents' fees the Football League has helped bring this about."