Forest boss Billy Davies has made Leadbitter one of his top targets this summer and he is thought to have firmed up his interest with an offer for the former Sunderland man.
Leadbitter, who joined Middlesbrough last summer on a free transfer from Ipswich, impressed at the Riverside last term and was named the club's player of the season.
The 27-year-old started his career at Sunderland before joining Ipswich in the summer of 2009 and he has established himself as one of the best midfielders outside the Premier League in recent seasons.
Boro boss Tony Mowbray would be loathe to lose Leadbitter with the player seen as central to his plans for the new season.
However, Forest are hoping their offer will persuade Boro to cash in on Leadbitter, with a number of other Championship clubs tracking him.