The online advertising market will face increased opposition in 2008, according to a report from Deloitte.

Users will treat web ads with growing antipathy throughout the year, while tracking technologies will attract the attention of industry watchdogs, predicts the consultancy's annual report.

Advertisers will have to make a strong case to win over the public, said Deloitte head of technology, media and telecoms Jolyon Barker.

"The sector should communicate the quid pro quo of internet ads for end-users, for example in the form of free content," he said.

"But the more successful online advertising gets, the more subject to regulatory scrutiny it will become."

And as debates over privacy and data storage grow, firms may be forced to tailor their activities to different national markets.

"Actively researching consumers’ preferences country-by-country, if necessary, may prove to be the most effective way of managing privacy concerns, " said Barker.

"Such diligence may seem expensive, but could be cheaper than dealing with litigation, heavy-handed government regulation or public relations battles with lobbyists."