Across the Football League, £12.7million was given to agents between July 2009 and June this year, an increase of £3.9m.
£10.1m of this was spent by Championship clubs, compared to £2.2m in League One and £400,000 in League Two.
"Given the current economic climate, it is worrying to the see such a significant amount leaking from the game," said Greg Clarke, chairman of the Football League.
"This year's figures demonstrate a considerable increase on those of last season and it is essential that clubs work to reduce this liability over the coming campaign."
Players signed during the period of the report were Michael O'Connor, Josh Wright, Rob Jones, Adam Boyes and Michael Raynes.
Jordan Spence, George Friend, Bondz Ngala, Donal McDermott, Brendan Moloney and Jim McNulty also moved to Glanford Park on loan.
Fourteen clubs did not give any money to agents, 11 of whom are in League Two with three in League One.