Academics have been warned to protect their intellectual property rights after a lecturer at the University of Bradford spotted her work for sale online.

Dr Judi Sture, head of the university's graduate school, was shocked to discover one of her articles for sale at American internet retailer Amazon.com for ten dollars.

Neither Amazon.com nor a third party had contacted Dr Sture to ask for her permission to sell the paper, which examined issues around biological anthropology and took three years to complete.

It has led Dr Sture to call for the closing of a "loophole" which allows such papers to be sold.

She said: "There appears to be a loophole that we are going to have to take advice on.

"Direct permission is definitely not being sought from academics to sell their research papers.

"The loophole appears to be that when we are sending research papers off to journals in good faith, they in turn have an agreement with licensing companies to sell them on.

"We are talking about research that took years of work being put up for sale on the web without the author's permission.

"When we have been selling pieces to journals we have been unknowingly giving away copyright."

Amazon.com has arrangements to sell academic articles through companies that secure the rights to research papers in journals from thousands of publishers worldwide.

Those arrangements are completely legal although Dr Sture believes it to be immoral.

She said: "It is not appropriate for people to be selling our work in places we have not chosen ourselves.

"I am not saying it would fly off the shelves but it is the principle.

"A lot of academics are not aware of this."

Dr Sture said she knows of other academics who had since spotted their work for sale on the website.

A spokesman for Amazon.com said the firm had a licence to sell Dr Sture's work through an American "content aggregator" called ProQuest Information and Learning.

He said: "We license content from various content aggregators, some of which secure rights to content from thousands of publishers.

"We rely on our aggregators and, in turn, our aggregators rely on publishers, to ensure that all articles are cleared to distribute online.

"Occasionally, there may be uncertainty between the aggregator and the publisher, or between the publisher and author regarding the electronic rights to an article."

ProQuest Information and Learning refused to comment about the sale of Dr Sture's work.

There is no suggestion that the UK Amazon website is selling academic articles.