Fortune 500 companies need to do more to ensure their websites are visible in search engine results, according to a new report from consultancy Conductor.

The New York organization’s study looked at the websites of firms in the Fortune 500 and discovered that only 28 percent of those surveyed had a presence in organic search listings.

Furthermore, just eight percent of companies were able to establish a mid to strong search result presence when it came to their most advertised key terms.

Conductor also said that businesses tended to deploy search engine optimization (SEO) tactics erratically across their various brands.

"When you consider the percentage of consumer activity that occurs in the natural search listings, these results should be something of a call to action for the biggest brands to concentrate more on how they structure data externally and SEO efforts," stated Conductor chief executive officer Seth Besmertnik.

Almost $5.1 billion was spent on search marketing by US firms in the first half of 2008, according to a report published by the Interactive Advertising Bureau last month.