England's money-spinning Premier League football clubs have seen their total revenue rise by 26% to nearly £2 billion, a report has claimed.
But Deloitte's annual review of football finance reveals the total debt among the 20 Premier League clubs hit £3.1 billion in 2007/8.
Wage costs also showed a record rise of £227 million - up 23% - to reach £1.2 billion.
According to Deloitte, Manchester United's debt now stands at £649 million and Liverpool's is at £299 million, both sums stemming from loans taken out by the owners to finance takeovers.
Arsenal's £318 million debt includes £250 million in long-term bonds taken out to finance their new stadium.
Alan Switzer, director in the Sports Business Group at Deloitte said: "Debt can be sustainable but football should not be complacent. They should make sure the business model works for them to make sure the level of debt is sustainable.
"The more debt you have, the more vulnerable you can be if you suffer a revenue knock-off such as failing to qualify for the Champions League or, in the worst scenario, relegation.
"Having a higher debt is not helpful in those situations and you have to make sure you have some flexibility, and that places an onus on having flexibility around player wages."
The increase in wage levels may also cause raised eyebrows but they do not appear a major problem as they are slightly less than the rise in income from Premier League TV rights. As a result the wages-to-revenue ratio improved slightly to 62% from 63% the year before.
Manchester United and Arsenal both paid out less than 50% of income in wages, and Liverpool 55%, but Chelsea's ratio was 81%.
