Interflora has filed a lawsuit to stop M&S and Flowers Direct from using 'Interflora' as a sponsored search term, as well as the misspellings 'Intaflora' and 'Inter-flora'.
The companies are not breaking any of Google's AdWord policies by bidding on the word. The search giant changed its policy on companies being allowed to bid on their rivals' trademarks in May. It allows advertisers to bid on any brand names, but prevents them from using a rival's trademark in the text of the ad that appears in the sponsored search slot.
A spokeswoman for M&S said that the company was "extremely surprised by Interflora's course of action", adding that it was industry-wide practice and not unlawful.
However, Interflora is arguing that the actions of M&S are a breach of trademark law.
Michael Barringer, marketing director of Interflora UK, told the website OUT-LAW.com: "The Interflora brand is extremely valuable and we will not tolerate competitors taking advantage of it and infringing our right.
"Throughout its history, Interflora has been forced to use legal means to prevent infringement of its valuable trade marks. This action represents only the beginning of a broader strategy to defend the Interflora mark against infringers."
The lawsuit was filed last week and at the time of writing, neither M&S nor Flowers Direct Online appeared to be using the keywords.
In the US, Nike filed a lawsuit against a company called Eastern Mountain Sports Inc, saying that its policy of bidding on the search term Dri-Fit on search engines including Google was an infringement of its trademark.