Campbell, who won 73 England caps, says that too many players receive an international call up before they have established themselves at club level.
Speaking on Football Focus, Campbell said: "Some of the young players have got their England careers far too early.
"It's far too easy for players who have not done much in the game to play for their country, it all connects and that's why results aren't going so well.
"When I started, I had to play top football for 18 months before I could get a look-in.
"Yes, I was in with the England side earlier than that but just training with the team and then I'd go back with the Under 21s.
"Now it seems like if you've played a few games, scored a few goals, cleared a few balls off the line and threaded a couple of really good balls in, all of a sudden you're in the England side."