Lobbying groups representing airlines, hotels and retailers have urged European Union tech regulators to ensure that Google takes their views into account, and not just large intermediaries, when making changes to comply with landmark tech rules.

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 had in March expressed their concerns about the impact of the new rules.

EU's Digital Markets Act (DMA) imposes a list of dos and don'ts on Google and five other tech giants aimed at giving users more choice and rivals a better chance to compete, but the groups voiced concerns the the adjustments could hurt their revenues.

In a joint letter to EU antitrust chief Margrethe Vestager and EU industry chief Thierry Breton dated May 22 they said their worries have mounted since then.

"Our industries have serious concerns that currently considered solutions and requirements for implementing the DMA could further increase discrimination," they wrote.

"Initial observations indicate that these changes risk severely depleting direct sales revenues of companies by giving more prominence to powerful online intermediaries due to the preferential treatment they would receive," they said.

The Commission, which is now investigating Google for possible DMA breaches, did not immediately respond to a request for comment.

Google, which in a March blog post said changes to search results give large intermediaries and aggregators more traffic and less for hotels, airlines, merchants and restaurants, had no immediate comment.

"We are concerned that the non-compliance investigation refers only to the need to treat third-party services in a fair and non-discriminatory manner, without any acknowledgement of European businesses that also offer their services on Google," the groups said.