Seven out of 10 companies that advertise online are unsure whether they actually get what they pay for, according to the Fournaise Marketing Group.
The tracking firm said that this figure reached 75 per cent in the UK and 78 per cent in the US.
Two-thirds of marketing departments indicated in a survey that they did not know whether they could trust the visitor/traffic profiles claimed by online media owners and publishers.
Fournaise believes that marketers have a "major trust issue" when it comes to the overall reliability and credibility of online advertising.
This lack of trust could be detrimental to all stakeholders, as the Kelsey Group's annual Global Interactive Report predicts that global interactive advertising will reach $147bn by 2012 from the current $45bn.
Some 40 per cent of respondents around the world did not run online campaigns in 2007, a figure which reached 65 per cent in high GDP growth markets such as Greater China, India and Singapore.
The report highlighted the top five concerns about online advertising:
This could explain why marketers are planning to take a prudent approach in 2008.
"Across the thousands of online campaigns we audit track for our clients worldwide, we have been observing consistently poor results," said Jerome Fontaine, chief executive of the Fournaise Marketing Group.
"Click-through rates have fallen as low as 0.15 per cent, conversion rates are barely reaching the three per cent average, and returns on marketing investment are flirting with the sub-30 per cent numbers."
Fournaise believes that online media has lagged behind for too long and that proper and full auditing is the key to winning the trust of advertisers, as with traditional media including print and broadcast.
"The discrepancy between what is claimed and/or purchased and what is actually delivered is beginning to cast a shadow on the long-term credibility of the industry," warned Fontaine.