The Manchester United manager believes football is heading for a financial catastrophe, mirroring the business world.

Ferguson explained: "I think there is an awful lot of expenditure and you say to yourself: 'Where is it going to end?'

"That is exactly what was happening in the business world two years ago. There were warning signs and everyone knew there were, yet they carried on because it was so easy to access loans.

"In the football world you say to yourself the warning signs are there, but nobody seems to be bothering about it.

"You wonder where it's going to go and what is going to happen if one major club are to go, to collapse."

Ferguson is uncomfortable with clubs who are sustained by rich owners - including neighbours Manchester City, who have spent extravagantly under the ownership of Sheikh Mansour.

United themselves have a debt of around £700million following the takeover of the Glazer family in 2005 - but Ferguson believes United operate within their means.

The Scot, interviewed by North West Business Insider magazine, continued: "People are treating football as an item for themselves, owning clubs with untold wealth that you wonder if it is really good for the game or good for that particular club.

"The clubs cannot complain because they see a possibility of richer rewards again. That has got to be the carrot.

"But it is not easy winning things. Definitely not easy, and they'll soon find out."