Google Inc. in October officially stopped offering for free the product listings that show up in Google search results when a shopper searches for an item. Now merchants bid and pay for ads, and Google chooses which retailers appear in Google Shopping results based on a combination of the ad’s relevance to the search term and the retailer’s bid. Microsoft Corp., owner of the competing Bing search engine, launched a national campaign this week to highlight that merchants pay for Google Shopping results, offering Bing as a more objective alternative.

The “Don’t Get Scroogled” campaign’s home base is a web site, Scroogled.com. Microsoft says the made-up verb describes “Google’s new practice that leaves people with fewer choices and potentially higher prices.”  The site includes a video that shows Google Shopping results and labels them as paid ads. The site also encourages consumers to submit their own “Scroogled” story on Bing’s Facebook page.

“We don’t let who pays us for ads or other services affect how your search results are ranked,” says Mike Nichols, Bing’s chief marketing officer.

The Scroogled campaign follows another Bing advertising effort that endeavors to highlight Bing’s search results. “Bing it On” debuted in September at BingItOn.com and asks consumers to submit search queries to see side-by-side results from Google and Bing. The search results are not labeled according to which engine generated them, and consumers are asked to pick the one they think provides the best results. A Bing-sponsored study used to support the campaign showed that, out of 1,000 participants, 57.4% chose Bing results more often, 30.2% chose Google more often and 12.4% resulted in a draw.

Two-thirds (66.7%) of all U.S. search engine queries went through Google Inc. web sites in September, according to comScore Inc. Sites that use the Bing search engine handled 28.1% of queries. Bing is used for all search queries submitted at Yahoo Inc.-operated sites and Microsoft sites like MSN.com.