Richard Scudamore has revealed the Premier League has turned down prospective buyers of clubs ''too many times to mention''.
The executive chairman of top-flight football in England also said the Premier League would not be concerned if all its club owners were foreign, as long as they had passed its owners' and directors' test.
Fifteen of the 20 Premier League clubs are currently foreign-owned, while an ever-increasing number of English Football League (EFL) clubs also have overseas investors.
Just this week Reading, who will bid to become a Premier League club again when they play in the Championship play-off final next weekend, announced they are to be taken over by a Chinese consortium. The ownership of Nottingham Forest also changed hands this week with Evangelos Marinakis, already the owner of Greek club Olympiacos, buying out Kuwaiti businessman Fawaz Al Hasawi.
The Premier League and EFL have been criticised for not doing more to protect clubs from foreign owners who have overseen unsuccessful and at times chaotic regimes at the clubs they control, but Scudamore insists the checks are stringent and thorough and that many fail to satisfy them.
Asked how many times prospective owners have been turned down, he told BBC Radio Five Live's Sportsweek programme: "Too many times to mention. I wouldn't have a count of them but it would run into the 10s and probably into the 20s.
"It's a very complex process. We have business intelligence companies that operate all around the world and we, the Premier League, spend an awful lot of money on this, it's a costly business.
"We delve right to the bottom and manage to find out things that the investment banks don't seem to be able to find out sometimes because we have very deep and resourceful intelligence networks.
"It should be of some reassurance to fans how deep and how hard we look at this, it's very extensive because ultimately they are only custodians for as long as they are here, the clubs are far more than just business assets.
"I think if you were to ask anybody who has come through our door in the past few years trying to buy a club they would probably admit to the fact it is so extensive.
"Sometimes it can take three weeks, sometimes it can take six or seven months. Sometimes it is pretty evident when they don't pass the first hurdle but sometimes it is much harder because many are very plausible in many cases.
"They must show they have the financial ability to run the club, although we have to separate that from incompetence and some people don't run clubs very well - but that's not what the owners' and directors' test is about.
"But as regards the number of foreign owners, it really isn't something we concern ourselves about. What we do concern ourselves with is the owners' and directors' test to make sure prospective owners behave properly, operate properly and work within the collective spirit of what the Premier League is and doesn't try to disrupt that.
"Basically do things as per the rules, which remember are a contract between the 20 Premier League clubs. Whether they are foreign or whether they are English I have no view on."
The EFL approved Marinakis' takeover of Forest despite an ongoing investigation into accusations of match-fixing in Greece - something the Olympiacos owner denies. He insists the accusations are politically motivated to discredit him.
Scudamore added: "I'm not going to talk about individual cases but we (the Premier League) work closely with the Football League on all of these matters and help support them financially with their investigations as well because we want the game in England to run to very similar tests. So we do have an influence, ultimately though the board of the Football League have their own decision to make."