Saints boss Nigel Adkins wants to sign the player he sold to the Parkhead club for around £2million in 2010 when he was at Scunthorpe. However, Lennon is keen to keep Hooper as he bids to win the Clydesdale Bank Premier League title back from Old Firm rivals Rangers.
"There has been another enquiry for Hooper this week," the Irishman was quoted as saying by a number of newspapers.
"But the valuation of that club and our valuation is some way off.
"I've no idea if Southampton will come back in. But they will get the same answer - that he's not for sale.
"Goalscorers are priceless. If you look at Gary's record in his time here, he's got a goal in every one-and-a-half games.
"He was one of the leading scorers in the Championship. When I went to see him he stood out like a sore thumb.
"I think it's been good business and he's enjoying life here and enjoying his football."