A BBC-led analysis, conducted with accountants Deloitte and football finance experts Vysyble, also found that despite the league bringing in its highest-ever revenue of £749m, overall spending on player and staff wages exceeded clubs’ revenue by 11 per cent.
It also revealed that more than half of clubs are spending more on wages than they make in income, with the figures prompting ex-Wigan Athletic chairman David Sharpe to express his concern that the Championship is a “bubble waiting to burst” with clubs posting record losses in a “gamble” to reach the Premier League.
Middlesbrough posted the highest pre-tax loss of the county’s second-tier clubs in 17-18 at £6.4m.
The losses would have been significantly higher if the club had not recouped £27.7m in player sales, including the exits of Ben Gibson and Adama Traore.
Leeds United (£4.3m) and Sheffield United (£2m) also recorded losses. Barnsley made a modest loss of £200,000 before tax.
Sheffield Wednesday and Hull were among five clubs to post a profit, but there were accentuating factors in the figures of both.
The Owls sold their ground to owner Dejphon Chansiri for £60m in June, allowing them to record a pre-tax profit of £2.6m for 17-18, which allegedly helped the club meet Profit and Sustainability (P&S) rules.
P&S rules introduced from the 2016-17 season allow the majority of clubs to make £39m in losses over three seasons.
Wednesday were charged with misconduct by the EFL last month, after an investigation into the sale of Hillsborough, which the league allege helped it meet P&S rules. The club have claimed that the charges are ‘unlawful’.
Hull recorded the biggest pre-tax profit of any Championship club in 17-18 at £23.7m, but it was reliant on the sales of several high-profile players such as Sam Clucas and Andy Robertson.
The highest losses were recorded by Wolves (£57.2m), Fulham (£45.2m) and Cardiff City (£39.3m).
Experts have warned that the spending gap between wages and revenue will reach an all-time high in the next set of Championship accounts due from 2018-19.