The 42-year-old has played Carla Connor since 2006 but she's apparently planning to walk out of Weatherfield for good next year.
A source told The Sun: "Bosses are reeling. Carla is a huge part of the show and they thought Ali wasn't going anywhere.
"She has been thinking about this for a while. She wants to go elsewhere and work on other projects. Carla's exit will be planned for early next year."
Alison's exit comes after several other of the ITV soap's biggest stars, including Michelle Keegan, 27, quit the show over the past year.
The insider continued: "Michelle Keegan, Chris Gascoyne and Julie Hesmondhalgh have all left in the past year.
"Corrie is still very popular but behind the scenes things aren't so good."
While Corrie bosses have yet to confirm Alison's exit, a spokesperson said: "Alison King has indicated to producers she would like to take a sabbatical from the show for creative reasons at some point in 2016.
"She wishes to try her hand at other projects before returning to the part of Carla Connor, a role she has enjoyed playing for nine years."
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