Marks and Spencer Group has purchased a 50% stake in Marks & Spencer Marinopoulos BV, which runs 38 M&S stores in Switzerland, Greece and Balkan states, including Romania and Bulgaria for 50m (38m).
The company plans to open up to 50 new stores in these markets over the next few years.
M&S plans to grow its international business to 15-20% of Group revenues within the next five years.
The Marinopoulos Group has been a partner of M&S for 30 years and has exclusive rights to operate M&S stores in Greece, Romania, Bulgaria, Serbia, Croatia, Slovenia and Switzerland under a franchise agreement.
It also has rights to operate in Austria, Bosnia and Herzegovina, the former Yugoslav Republic of Macedonia, Albania and Montenegro where, currently, there are no M&S stores.
M&S director of international business Carl Leaver said: "We have an exciting opportunity to open many more M&S stores in Greece and the Balkans and our joint venture with Marinopoulos will mean we can really put M&S on the map in this part of the world.
"In Greece, we already have a solid platform to build on and there is a growing demand for great quality, good value M&S products in markets like Romania and Bulgaria.
"We have worked with Marinopoulos for over 30 years and their retail expertise and local knowledge make them the ideal partner for us."