BRUSSELS, March 6 (Reuters) - Lobbying groups representing airlines, hotels and restaurants on Wednesday warned that changes proposed by Alphabet's Google to comply with EU landmark rules may drive users to large online search services at their expense.

The comments from Airlines for Europe group that has Air France KLM and British Airways owner IAG as members, hotel group Hotrec, European Hotel Forum, Eurocommerce, Ecommerce Europe and Independent Retail Europe came after Google rolled out changes for app developers and users.

Google together with five other tech giants have to be fully compliant with a list of dos and don'ts set out under the Digital Markets Act (DMA) on March 7.

"It should not lead to situations where the economic power of large online intermediaries is further entrenched and where consumers are not presented with a variety of choices," the groups said in a joint statement about the planned changes.

Some of the companies could lose as much as 50% of their online traffic and possibly millions of euros in revenues due to Google's changes to its search results, people with direct knowledge of the matter said.

Google declined to comment. In its blogpost on Monday, it said changes to search results give large intermediaries and aggregators more traffic and less for hotels, airlines, merchants and restaurants.

Lobbying group eu travel tech which counts Amadeus , Booking.com, Expedia and Airbnb as its members, in turn criticised Google for allegedly continuing to favour its products over rivals despite DMA rules seeking to rectify that.

"Google continues to self-preference its own intermediation services on the search engine results page. In travel search, this includes the display of Google's comparison products for Hotels, Flights, Things to do, Trains and Vacation rentals with units that are more prominent, interactive and rich than any other search result," they said in a joint statement. (Reporting by Foo Yun Chee Editing by Tomasz Janowski)