The ex-Coronation Street star, 32, will bow out of the hit show, which sees her play British Army medic Georgie Lane, with a final series later this year.
The Stockport-born actress has left in a bid to pursue new acting jobs and plans to spend more time at home in the UK after her husband Mark Wright, also 32, moved back from Los Angeles last year, where he was working on US TV.
She had previously spent several months each year filming in far-flung locations including South Africa, Nepal and Malaysia.
Michelle told the Sun: “I’ve had the most incredible four years on the show and I want to thank the BBC for giving me such an amazing opportunity.
“Playing Georgie has been a life changing role for me. I’ve loved every second of the adventure so it was a very hard decision to make not to return. I feel it is the right time to explore other exciting opportunities but I’m so happy to be part of the new series coming soon so it’s not the end just yet.”
Producers are currently looking for another female to play the lead in the hit series, which starred former EastEnders actress Lacey Turner, 31, for its first run in 2014.
Michelle spent much of last year shooting her third series of the drama and more recently has shot a second series of Sky1 comedy Brassic and continued her lucrative clothing deal with online retailer Very.
The actress, who wed telly host Mark in 2015, will now be freed up to spend more time near their home in Essex.
But last year she revealed she was sick of “everybody’s obsession” with her becoming a mum in the near future, including from her friends and family.
She said: “It’s horrible. It’s like, ‘You’re 32. Are you not planning to have a baby yet?’
“They don’t know the background of what’s happening. It’s no one else’s business. In this day and age you shouldn’t ask questions like that.
“I get so frustrated. I’m asked purely because I’m a woman. But I’m immune to it now — it’s like a reaction and as soon as I hear it I brush it off, as it’s no one else’s business.”
Source : thesun.co.uk