M&S Outlet offers more than 1,300 clothing products across womenswear, lingerie, menswear and kidswear, and now has 50 stores after launching in November 2000.
The ranges will be available via a microsite hosted at www.marksandspencer.com/outlet and will be regularly refreshed with products from recent M&S collections, with discounts of up to 40% on the original price.
Richard Fox, head of M&S Outlet, said: "The internet is often the first port of call for shoppers in search of a bargain, as it offers a quick and convenient way to compare the deals available.
"We've responded to our customers' increased demand for online access to great value, by extending our popular Outlet offer on our website."
M&S will offer free delivery to customers spending £30 or more on the microsite up until Sunday 4 March, in order to drive growth.
Customers who are signed up to the M&S newsletter will get 10% off their first order on from M&S Outlet online.
Follow Matthew Chapman at @mattchapmanUK