By Sean Coughlan
BBC News education reporter
Google is to ban adverts for essay writing services - following claims that plagiarism is threatening the integrity of university degrees.
Google is blocking adverts where essays sell from �5 to �5,000
There have been complaints from universities about students being sold customised essays on the internet.
The advert ban from the Google search engine has been "warmly welcomed" by university authorities.
But it has angered essay writing firms which say this will unfairly punish legitimate businesses.
From next month, Google will no longer take adverts from companies which sell essays and dissertations - and the internet company has written to advertisers to tell them about the policy.
Google's forthcoming ban on adverts for "academic paper-writing services and the sale of pre-written essays, theses, and dissertations" means that essay websites join a blacklist of "unacceptable content" including adverts for weapons, prostitution, drugs, tobacco, fake documents and "miracle cures".
The move has been applauded by universities which have struggled with the problem of students dishonestly submitting material copied from the internet.
Universities warn that plagiarism "devalues" higher education
"Making life harder for these cynical web 'essay mills' is a step in the right direction," says Professor Drummond Bone, president of Universities UK.
"We welcome this move. Essay writing sites claim that students pay hundreds of pounds for model answers - but do not then submit these as their own work. We all know this claim is absurd."
The universities organisation says that in particular there have been difficulties with essays bought by students from companies which sell tailor-made answers, where fees can be up to �5,000 for a single piece of extended work.
There have been reports of up to 12,000 essays being sold to students in a year, says Universities UK.
These essays and assignments can be written by freelance academics or other students - and it is less easy for plagiarism software used by universities to detect such work.
Google, commenting on the change, says its advertising policies are "developed and evaluated based on multiple factors, including legal and cultural considerations plus user and customer experience".
And a spokesperson said that the advert ban was expected to be applied across Google's global network.
But one of the UK companies fearing that it will be prevented from advertising, Essaywriter.co.uk, is angry at the threat to its business - with 80% of its customers coming through Google.
Managing director Matthew Wilson says this will punish the legitimate, transparent companies, which sell essays, but which warn students that they must not be used dishonestly.
Mr Wilson says that such a bespoke service, selling tailor-made essays at short notice, with prices around �70 and upwards, can be used as a guide for students wanting extra assistance.
Overseas students are frequently customers, he says - but the firm makes clear that essays should not be passed off as being written by the student.
And he says that such a blanket ban will not stop the search engine from generating links to rogue essay selling companies, which have been accused of scamming customers by providing poor quality material.