Talks are believed to be ongoing over a deal for the 23-year-old, who has been told he can leave to seek more regular football.
Milan are keen to bring Tomori in to boost their Serie A challenge in the second half of the campaign – and have been encouraged by Chelsea’s willingness to let him go.
But Lampard, who worked with the player at Derby before taking over at Chelsea, has made it clear that any move will only be on a temporary basis amid suggestions in Italy that a deal could include an option to buy.
He said: “He absolutely has a long-term future at this club and we will see if and when he goes out on loan.
“The moment I got close with Fikayo is when I took him on loan to Derby and he was the player of the year and one of the best players in the Championship that year.
“He came back last year, played 20 plus games for us at a young age and then got in the England squad.
“There is a long-term plan for Fikayo in my head about his career here. And if he goes out on loan it will be to enhance his personal development, hopefully, help the team he goes to, and come back as a better player.”
Tomori has made only four appearances this season, with his only starts coming in the Carabao Cup.
The arrival of Thiago Silva last summer has pushed him down the pecking order, with Kurt Zouma, Antonio Rudiger and Andreas Christensen also ahead of him.