Despite concerns over the expense, it is crucial that small and medium-sized enterprises (SMEs) invest in search engine marketing, it has been claimed.

According to Ben Potter, sales director at search engine firm Leapfrogg, the cost of search engine optimisation advice remains lower than other advertising mediums.

"I believe there to be a closing window of opportunity for some SMEs to get online before ever-increasing competition, and therefore costs, push search out of reach for those with limited resource," he said.

Research by Microsoft adCentre conducted by Vanson Bourne found that three-quarters of SMEs reported increased sales after investing in search engine marketing.

Despite this figure, only three-fifths of companies were found to actually invest in this form of advertising.

The study also found that in the UK alone, SMEs are "wasting" around £3 billion by advertising on websites that are "virtually invisible" to consumers.

Reasons for not investing in search engine optimisation were cited as high costs, complications and time constraints.