Bennett has made over 100 appearances for Town as a teenager
Peterborough United director of football Barry Fry has revealed Posh are interested in Grimsby defender Ryan Bennett and have had an offer rejected.
Grimsby boss Mike Newell named the 19-year-old as club captain this season.
Fry told BBC Radio Humberside: "Grimsby have got a option on the boy and said 'thanks for the interest but we wouldn't sell him for £1m'.
"Ryan fits our bill as a young hungry talent. Grimsby feel the same way and want to keep their best players."
Posh boss Darren Ferguson recently transfer-listed 12 squad players and has already swooped for Stockport winger Tommy Rowe.
I've had three different agents talking about Ryan. I don't know who he's represented by or whether he's got one agent, or two, or three, or none
Peterborough director of football Barry Fry
He will be keen to add to his central defensive options with Chris Westwood, Kieran Charnock and Shane Blackett all being told they are surplus to requirements at London Road.
Fry admits that Bennett, who was named Grimsby's fans' player of the season and has an England Under-18 cap, may be in the middle of a tug-of-war between football agents.
"I've had three different agents talking about Ryan. I don't know who he's represented by or whether he's got one agent, or two, or three, or none," Fry said.
"You find at this stage of the season there are many agents calling clubs up and if you seem interested then that agent will ring Ryan and say 'if you come and join me I can get you a club and all that'."
Bennett has made over 100 appearances for Grimsby, including 76 league starts.
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