The UK's Advertising Standards Authority (ASA) has called on ISP Freeserve (now known by the brand name Wanadoo) to make clearer to users which of its web search results are paid advertisements.
The ISP, owned by France Télécom, uses pay-for-placement listings from paid search service provider Overture, which the ASA said is set up in a manner that consumers may find confusing.
In its adjudication, the ASA wrote: "Because sponsored links were not clearly identified by a headline or title, and the search page did not contain an explanation of the purpose of the hyperlink, the authority considered that consumers were unlikely to realise that the Overture hyperlink indicated that results were sponsored and concluded that consumers could be misled.
"It asked Freeserve to ensure that sponsored links were clearly identified in future."
The ASA has no regulatory authority but can refer cases to the UK's Office of Fair Trading.
"We are looking closely at the ASA's request and have no further comment at this time," a spokeswoman from Wanadoo in the UK said.
Laura Rohde writes for IDG News Service