Holiday review site Trip Advisor has joined the swelling ranks of firms complaining to the European Commission about Google.
It joins travel firm Expedia and 11 others in accusing the search giant of abusing its dominant position, a claim being investigated by the commission.
EU commissioner Joaquin Almunia said a decision would be made after Easter over whether to formally charge Google.
Google denies claims of "anti-competitive and unfair practices".
Trip Advisor's statement said: "We hope that the commission takes prompt corrective action to ensure a healthy and competitive online environment that will foster innovation across the internet."
In response Google said: "We've been working closely with the commission to explain how our business works since their investigation began. We haven't seen this complaint yet, but will continue to discuss any concerns with the commission, knowing that there's always room for improvement."
Google Places, which offers reviews of hotels and restaurants, has put the search giant into direct competition with travel firms such as Expedia and Trip Advisor. Google also launched a flights search tool in September 2011.
The current EU probe was kickstarted in February 2010 by specialist search engine Foundem. It alleged that Google's algorithms "remove legitimate sites from [its] natural search results, irrespective of relevance".
It also said that the firm promoted its own services over those offered by competitors. Since then the commission has received a flurry of similar complaints.
In November 2011, it announced that it would investigate.
Google offers two types of search result - unpaid results produced by the firm's algorithms that are displayed in the main body of the page and "ads", previously called sponsored links.
The EU investigation is attempting to determine whether the firm's method of generating unpaid results adversely affects the ranking of other firms, specifically specialist search providers known as vertical search services.
Google is facing similar attention in the US, where a Senate subcommittee and the Federal Trade Commission are looking at whether it abuses its market position.
Rival Microsoft faced years of similar anti-trust investigations which culminated in heavy fines.