Following successful pilot schemes, the retail giant plans to roll out the projects it runs in conjunction with the charity Business in the Community.
Up to 200 homeless people are to be offered two-week's work experience this year at stores in Leeds, Nottingham, Bristol, Liverpool, Birmingham and Manchester.
More cities could follow. "We have identified other areas where we would like to run the scheme but Business in the Community hasn't got programmes there so we need to work with them on that,
said M&S community involvement manager Freda Pinner.
M&S is also finalising plans to offer similar opportunities to prisoners after operating a small trial scheme in Norwich involving low-risk prisoners who were on the verge of being released.
Pinner added: "We are in talks with the prison service but obviously this one is a bit more difficult to handle because we have to get buy-in from the stores and be confident that the prisoners really do want to work with us."
Those given placements will work alongside staff "buddies
who guide them through the working day.
When M&S ran a homeless project last year in London, it resulted in a job for one of the eight intake, albeit at a different company. Once placements end, the company will continue to help them search for jobs.
The company has a long history of community service through initiatives such as its food donation scheme to the homeless.