The forward joined City from Cambridge United two years ago but will be allowed to leave for a cash sum so that new players can be brought in.
City are reported as asking around £400,000 for Simpson who has triggered an extra year option at the Sky Blues.
Like most managers at this time of year, Brighton boss Russell Slade who kept Albion in League One is keeping quiet about his transfer targets and told the Brighton Evening Argus that he is refusing to speak about speculation.