Musselburgh Joint Racing Committee, which runs the course, wants to create an all-weather track, extend the grass track and erect floodlights.
Supporters claim it would boost the town's economy and create jobs.
But the scheme has provoked objections about its effect on the Musselburgh Old Course, an historic golf links situated within the racetrack. There are also fears over traffic congestion and the future of the nearby Ash Lagoons wildlife sanctuary.
The scheme was approved by East Lothian Council in March but was subsequently called in by ministers, dashing hopes that work could start this month.