The stores are in Monks Cross (near York), Portsmouth, Slough, Warrington, Wokingham and Worksop.
M&S said it was consulting the 380 affected workers and it is expected they will be able to move to nearby outlets.
"It is our intention that nobody leaves M&S and we will work as hard as possible to ensure that we can deliver against this promise."
He added: "Our customers' shopping habits are changing.
"We will open new stores, some will reduce in size, some will move, some will close and others will convert to food-only."
The retailer had already announced it would open 36 new stores over the next six months, creating more than 1,400 jobs.
Of these, 34 will be food-only - including Bishopsgate in London, Huntingdon, Aylesbury, Spinningfields in central Manchester and Strood in Kent.
Of M&S's 959 current stores, 615 are food-only.
The two new locations for M&S with clothing, home and food are Bracknell and Rushden.
The news comes just a few months after M&S reported a better-than-expected 2.3% third-quarter increase in like-for-like sales for its beleaguered clothing and home division, while food climbed by 0.6%.
M&S said in November its five-year plan was to close about 30 UK stores and convert 45 more into food-only shops, while also announcing a retreat from some international markets.