The Labour MP for Bassetlaw, who made the claims on Twitter, said patients would have to travel nearly 20 miles to Doncaster Infirmary for treatment.
It comes after hospital chiefs admitted they were having to make cutbacks due to a £12million “black hole” in the hospital’s finances.
Mr Mann has urged residents to sign a petition protesting against the “closure” of the unit, which opened in 2011.
He said: “I backed the plan for the opening of the breast care unit at Bassetlaw because women want to be treated close to home at this difficult time in their lives. We need to campaign against this cut.”
The Guardian has contacted Bassetlaw Hospital for comment.
More to follow.