WASHINGTON DC: Leading search engines in the US – including Google, Yahoo and Microsoft – have been accused of making it difficult for users to distinguish between ads and organic search results.

An article in the Wall Street Journal has suggested that the three leading US search engines have done little to comply with a requirement issued by the Federal Trade Commission (FTC) that they do more to highlight ads in search results.

Mary Engle, the FTC's associate director for advertising practices, wrote to 22 search sites in June 2013, warning them that they risked misleading consumers because of a "decline in compliance".

She specifically urged the search sites to include more prominent shading for ads and to label them "explicitly and unambiguously".

However, the article went on to say that Google now simply displays a small yellow "Ad" label next to some paid links while the shading of ads on Yahoo and Microsoft's Bing search results "is nearly imperceptible".

The Wall Street Journal also included "then and now" graphics of search results to illustrate how ads are being labelled.

"Consumers are being tricked," asserted Robert Weissman, president of Public Citizen, a consumer-advocacy group.

All three main search engines responded to the accusation, insisting that they clearly distinguish ads from organic search results.

Yahoo said it believed its "practices in displaying search results to be consistent" with FTC guidelines. Microsoft said it had "instituted clear labels to distinguish ads from organic search results".

Meanwhile, Google said it has "always prominently labelled advertisements".

Mary Engle declined to say whether the FTC is considering enforcement action or if it has taken up the issue with the search engines concerned.

Data sourced from Wall Street Journal; additional content by Warc staff