NEW YORK: The US Federal Trade Commission has written to 24 leading online search engines, including Google, Bing and Yahoo as well as specialised search providers, warning them of the need to offer a clearer distinction between organic and paid search results.

The agency stated that "paid search results have become less distinguishable as advertising, and the FTC is urging the search industry to make sure the distinction is clear".

This was necessary, it said, in order "to avoid the potential for deception". So consumers "should be able to easily distinguish a natural search result from advertising that a search engine delivers".

As part of its case, the FTC cited a 2012 survey by which found that around 50% of search-engine users didn't recognize that the ads at the top of a page of search results were not part of the unpaid, organic search results.

Such ads have been typically differentiated by background shading but the agency suggested that this was often too light to be clearly visible to users.

It offered new guidance how to achieve this, including the use of visual cues, labels and other techniques in order to avoid consumers being misled. A failure to follow the rules could conceivably result in fines being levied.

A Google spokeswoman told the Wall Street Journal: "Clear labelling and disclosure of paid results is important, and we've always strived to do that as our products have evolved."

Yahoo welcomed the guidance and said it was reviewing it, adding: "We have always been committed to providing a clear and transparent search experience for our users".

The FTC also addressed developments such as voice interfaces and recommended "audio disclosure" of results based on payments by a third party.

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