LONDON: Most ad formats are less trusted now by UK consumers than they were two years ago, with, paradoxically, the few registering an increase in trust being the ones that have been least well regarded, according to new research.

Nielsen's latest biennial Global Survey of Trust in Advertising polled 30,000 online respondents in 60 countries and found that, in the UK, 13 of the 19 ad formats considered had seen a decline in trust since 2013, while three had seen no change.

Trust in ads on social networks, however, had edged upwards one point, while that in text ads on mobile phones was up two points and ads on mobile devices up three points.

These three were also at the bottom of the list of most-trusted ad formats, with only around one third of respondents expressing any confidence in them. Text ads on mobile phones (27%) scored worst, while ads on mobile devices (33%) and ads on social networks (34%) were only slightly better.

Those figures contrasted sharply with the most-trusted format: personal recommendation – trusted to some degree by 81% of UK respondents – is by far the most trusted form of advertising or communication, with the credibility gap widening between it and other formats.

It now stands alone as the only format trusted by more than 60% of UK respondents, Nielsen noted, an accolade which was shared by five formats just two years ago.

"Consumer opinions online" (58%) is now the second most trusted format (up from fourth two years ago), followed by "emails signed up for" and TV ads (both 56%).

The format hit by the biggest decline in trust has been editorial content (down eight points to 54%) and the IAB has just published a set of guidelines to help the marketing industry provide more transparency to consumers around digital advertorials. These include the use of prominent visual cues and appropriate labelling.

Other formats that consumers were rapidly losing faith in were emails they had signed up for (down seven points to 56%) and newspaper and radio ads (both down six points to 50% and 51% respectively).

Online video ads (35%) and online banner ads (34%) have a lower trust rating than traditional ad formats, but their credibility has held up over the last two years.

Terrie Brennan, evp/marketing effectiveness for Europe, Nielsen noted that "about a third of online advertising campaigns don't work", as they fail to generate awareness or drive any lift in purchase intent and suggested that "a mix of both offline and online channels usually offers the best ROI".

Data sourced from Nielsen, IAB; additional content by Warc staff