The Advertising Standards Authority is urging six UK universities to avoid exaggeration claims that are used only to attract students. The advertising watchdog has told Leicester, East Anglia, Strathclyde, Falmouth, Teesside and the University of West London to scratch any misleading marketing claims. Chief executive Guy Parker says students need "good evidence" when making such a big financial commitment.

"Misleading would-be students is not only unfair, it can also lead them to make choices that aren't right for them," said Mr Parker.

Nick Hillman, director of the Higher Education Policy Institute, said that intensifying competition between universities now has a "touch of the Wild West about it".

"Universities should be careful about their claims, which need to be robust, truthful and useful.

"But it is a good thing that they are telling potential applicants more than they used to in the past."

The watchdog seeks to obtain a clearer description of the universities' achievements in rankings and league tables. "If you're making claims about your national or global ranking, student satisfaction or graduate prospects, make sure you practise what you teach... by backing up your claims with good evidence," said the head of the watchdog, Mr Parker.

"We don't set out to mislead or confuse prospective students," said a statement from the University of Leicester.

"We strongly believe that the marketing message was accurate, but we respect the decision of the Advertising Standards Authority," said a spokesman for Teesside University.

Charles Heymann, a higher education communications adviser, said that rankings could "exaggerate very marginal differences between individual universities.

"It's tempting for marketing teams to push the boundaries as far as they can go in emphasising them. At some point, most universities will be in the top 10 or 25 for something."

A spokesman for Universities UK said: "With a proliferation of university rankings, data and awards now in existence, there is a need for clearer guidelines for universities in how they use this in a way which is clearly understood by students."