Fulham academy boss Huw Jennings admits he has seen spies from Far East betting syndicates at youth games.
The Premier League has written to clubs warning that illegal betting syndicates are targeting academy matches.
"We have seen (these) people and, along with other clubs, contacted the league and informed them," the ex-Premier League youth boss told 5 live Sport.
"If we get involved in gambling on events involving youth, it's a really, really serious state of affairs."
Earlier this month, league secretary Mike Foster urged clubs to be vigilant for spies who were relaying information live from matches.
His letter referred to an individual operating on behalf of a Hong Kong betting syndicate who had been challenged at an Under-18 academy match, which 5 live Sport understands to have involved Leeds United.
There were other examples of this happening at academy matches, especially in Scotland, according to the letter.
"We must do all we can to stamp out illegal betting at youth games," Foster concluded.
Jennings said he first became aware of the practice when he was head of youth development at the Premier League.
He explained how betting syndicates would send informants to matches to relay information back to their bosses in the Far East, who would then place bets on the matches.
"Informants come and try and get into games and commentate to provide opportunities for betting," Jennings said.
"Usually you have got a young man trying to conceal himself, commentating into a mobile phone and trying to do it without detection.
"It's not healthy and we need to be very vigilant and challenge people appropriately.
"You have to have your wits about you. Our security and staff will be trying to ensure that if we see them we challenge them and they are evicted."
Jennings said he had no knowledge of academy players being approached by representatives of the foreign syndicates.
"We are not aware of that, because very rarely do they (the
"spies") try to reveal themselves. It is very much done on teams rather than individuals."