Town spent £280,000 on agents' fees during the first six months of 2008. The figures are revealed in the latest edition of the Football League's Agents' Fees Report.
That figure relates to 22 transactions, eight new registrations, two updated contracts, six cancelled contracts and six loans.
Only three Championship clubs paid agents more cash than the Blues during that period, relegated Leicester City (£519,355), promoted Stoke City (£385,000) and QPR (£310,000).
In total for the year July 2007 to June 2008, the Blues spent £405,000 on agents, the seventh highest figure in the Championship.
Overall, during the period July 2007 to June 2008 payments to agents from Football League clubs fell as a proportion of total transfer spending to 14%. Payments to agents in the same period a year ago was 19% of total transfer spending.
Football League clubs' expenditure on players has risen by 78% to £81.5 million over the last year, a figure which is more than two and a half times the level spent two years ago.
Football League chairman Lord Mawhinney welcomed the drop in payments to agents: "In the last 12 months we've seen a resurgent transfer market with clubs spending significantly greater sums on players.
"It is encouraging that this has not been coupled with a similar increase in payments to agents. Instead, these are now at their lowest levels since we began publishing these figures four seasons ago.
"Football League clubs continue to make genuine strides towards putting their economic affairs in order. We have led the way in this regard, though more remains to be done."
The full report can be viewed here.