M&S has acquired 51% of Coms for €13.6 million (£10.6m) in cash plus a deferred consideration of up to €5.2m (£4m) based on business performance and the achievement of agreed targets.
Coms operates 13 M&S stores in the Czech Republic, Slovakia, Latvia and Lithuania. The joint venture plans to open around 30 stores in these markets, together with Estonia, over the next few years.
M&S plans to grow its international business to 15% and 20% of group revenues within the next five years.
Carl Leaver, director of international business at M&S said: "There is a great opportunity to open many more Marks & Spencer stores acrosss Central and Eastern Europe and grow a real presence in the region. The Marks & Spencer brand is all well-recognised in the Czech Republic and there is increasing demand for good quality, great value products in markets like Slovakia. We have worked with the Coms team since 1996 and their retail expertise and local knowledge make them the ideal partner."
Separately M&S' men's underpants came top in a Which? survey. The Real Cool Cotton Trunks which retail for £5 beat rivals underpants in a 10-wash quality and longeivity test.