Hodgson does not want to block the development of youngster Chris Smalling.
Campbell was linked with several Premier League clubs after leaving Portsmouth in the summer, but instead joined Notts County.
“He was offered to us, of course, when he was thinking of leaving Portsmouth, like every other club I imagine,” said Hodgson on Sky Sports News.
“But we’ve got a player here called Chris Smalling, who is 19 years of age and is a current England Under 21 international. I think he’s got a very bright future.
“We’ve also got Chris Baird, who I think is a very fine player and it would be wrong to start bringing in players whose career is more behind them than in front of them because what it’s going to do is push, in particular, Chris Smalling back a further pace and maybe we’ll never get to know how good he can be.
“Sometimes if you’ve got a young player who you believe in, you’ve got to turn down the safer, more experienced option because otherwise the player will never get the experience.
“At the moment I’m quite happy with Smalling, Baird, Hughes and Hangeland, and I don’t think signing a fifth one would be a great advantage of us.”