More than 70 percent of Internet users leave their favourite Web sites because of intrusive or irritating ads, which especially appear on gambling sites, financial services firms, automobile companies, household goods and beauty product companies, Brand Republic reported Wednesday.

The figure grew to 84 percent for 24- to 34-year-olds, up by 20 percent since last year.

Nearly 60 percent of all Internet users stopped going to certain sites because of adverts, compared to 43 percent in 2007, according to independent research done by Opinion Matters for HowTo.tv, Brand Republic reported.

Meanwhile, 83 percent of 16- to 24-year-olds and 74 percent of 25- to 34-year-olds watch online video content, which might mean that video ads may be more effective for targeting younger audiences.

Fifty-six percent of those ages 16 to 24 and 44 percent of 25- to 34-year-olds said video ads were more likely to make them purchase a given brand. Only 38 percent of those ages 35 to 44 and 29 percent of those ages 25 to 54 shared the same opinion, reported Brand Republic.

"The difference in behaviour between younger and older web users is testament that the mass audience model is a strategy that doesn't necessarily work in the online environment, and is one that risks alienating web users and negatively impacting on propensity to purchase," said Russell Goldsmith, HowTo.tv's co-founder and digital director, according to Brand Republic.

888.com, Dulux, Ford, Halifax and L'Oréal were all considered to have “annoying” or “intrusive” ads, Brand Republic reported.

"The industry must re-examine what the web does best and create content that is relevant and entertaining, and that plays to consumer interests," said Peter Mitchell, WWAV Rapp Collins Media Group chief executive.

The research polled 1,046 individuals above age 16.