Exams watchdog Ofqual has issued a warning to all pupils in England against relying on Wikipedia as a research tool for their coursework.
In guidance sent out last week, the regulator said information from online resource sites such as the popular free online encyclopedia may not "be authoritative and accurate" and, in some, cases "completely untrue".
The comments were made in publications issued to teachers, parents and carers, as well as pupils, giving advice about authenticating learners' work and correctly referencing sources.
The report does emphasise, however, that search engines such as Google and Yahoo can be excellent sources for information because they pool material from numerous sources, based on learners' "keyword" searches.
Alf Wilkinson, national history head for new secondary curriculum at The Historical Association, said: "Ofqual rightly identifies Wiki-pedia's quality as variable and dependent on the knowledge and understanding of the contributor of each article. Part of the beauty of the internet is anyone can post anything, and it is likely to contain contrasting statements, ideas and interpretations.
'Bad' websites can be as useful as 'good' websites, as long as we give pupils the skills to weigh up arguments, make sure they are supported by evidence and reach their own conclusion.
"Wikipedia is no better, or worse, than Google. Pupils need to develop critical faculties when using the web. They readily question evidence in a textbook, but often accept what is online at face value.
"It is an issue, and Ofqual is right to point out that Wikipedia on its own is not enough. But neither is any single source. Most history teachers are aware of this issue and try to encourage critical use of web sources."
One guide, Using Sources: A Guide for Students, concedes that Wikipedia is useful for pupils researching assignments, but warns they should "never use it as your only source."
Mike Peel, chair of independent wiki support group Wikimedia UK, agreed with the watchdog. "The report contains fantastic advice on how to use Wikipedia as a starting point for research," he said.
"What you should never do is use content directly. It should be a stepping stone for going to other websites. I was taught at school, as a rule, to never reference an encyclopedia as a source, be it Britannica or Wikipedia. Every (Wikipedia) article should have references, with links to other sources."