Sheffield Wednesday spent just over £1.7m on agents fees between February 2017 and 2018, figures released by the Football Association show.
With the 24 Championship clubs spending just over £42m on agents, that works out at an average of £1.75m per club - but 12 actually spent more than Wednesday. Aston Villa led the way with a stunning £5.51m spend on registered intermediaries.
Sunderland, still in danger of relegation to League One, remarkably spent £4.37m on agents. Wolves, who look set to win the Championship title, spent £2m - less than struggling Birmingham - while play-off chasing Bristol City and Millwall shelled out £843,000 and £311,505 respectively.
Wednesday signed six players in the period concerned and extended the contracts of a number of their young players.
Nationally, Liverpool spent £26.7million on fees for intermediaries and agents - and Premier League clubs overall topped the £200million mark for the first time.
The figures showed that Liverpool paid out more than any other club, closely followed by reigning Premier League champions Chelsea and this season's table-toppers Manchester City.
Jurgen Klopp's team have been strengthened by big-money signings including Mohamed Salah, Virgil van Dijk and Alex Oxlade-Chamberlain over the past year, with agents also significantly benefiting from player transfers involving the club.
Chelsea spent £25.1million for the period concerned, taking in last year's summer transfer window and the recent January window.
Manchester City had an outlay of £23.4million and Manchester United paid £18million, the FA said, with the total Premier League spend amounting to £211,011,187, up from £174,227,243 for the corresponding 2016/17 timeframe.
Watford's total of £13.3million meant the Hertfordshire club were the fifth highest spenders, forking out more than Everton and Arsenal.
Of the current Premier League sides, Huddersfield were the lowest spenders with a total of £2.4million. Four teams currently in the Sky Bet Championship paid out more, with Aston Villa spending £5.5million, Middlesbrough £2.5million, Reading £2.8million and Sunderland £4.3million.
The aggregate spend by Premier League and Football League clubs amounted to £257,680,542, with Championship sides paying £42.183million. Clubs from League One paid £3.527million, and League Two outfits spent £958,969.
Much of the spending will comprise payments made to agents for transfers completed and contracts negotiated over the 12 months, although the FA said some payments may have been made for deals agreed before last February.
League Two side Crawley were the lowest spenders of all, with a £4,680 total investment.
Full Championship league table of agent payments:
Aston Villa - £5,510180
Barnsley - £419,639
Birmingham City - £2,461,909
Bolton Wanderers - £223,432
Brentford - £1,690,415
Bristol City - £843,174
Burton Albion - £268,490
Cardiff City - £2,026,917
Derby County - £2,180,305
Fulham - £2,428,175
Hull City - £1,882,530
Ipswich Town - £241,969
Leeds United - £1,349,452
Middlesbrough - £2,538,840
Millwall - £311,505
Norwich City – £2,212410
Nottingham Forest - £1,141,512
Preston North End - £1,046,679
Queens Park Rangers - £1,817,113
Reading - £2,850,283
Sheffield United - £652,070
Sheffield Wednesday - £1,714,130
Sunderland - £4,370,897
Wolverhampton Wanderers – £2,001,023