The submission of school projects using text and images lifted wholesale from the internet is becoming an increasing problem for teachers.

A survey by the Association of Teachers and Lecturers found that 58 per cent of teachers described web plagiarism as a problem.

Some 28 per cent of these teachers estimated that at least half of the work returned by pupils included content simply copied and pasted from the internet.

The survey polled 300 teachers at school sixth forms, sixth form colleges and further education colleges across the UK.

A teacher from Leeds described one piece of work as "so blatantly cut and pasted that it still contained adverts from the web page".

"This survey highlights one of the risks of putting so much emphasis on passing tests and getting high scores at any cost," said Dr Mary Bousted, general secretary at the Association of Teachers and Lecturers.

"Unsurprisingly pupils are using all the means available to push up their course work marks, often at the expense of any real understanding of the subjects they are studying."

The survey suggested that 90 per cent of teachers are concerned about the impact of plagiarism on students' long-term prospects.

Bousted warned that it is the pupils themselves who are the real losers as " they lack the skills they appear to have".

"Schools and colleges need to have robust policies to combat plagiarism, but they also need help from the exam boards and government with resources and techniques for detecting cheating," she said.

Plagiarism is a problem for teachers because it can be difficult to spot, and time consuming to identify.

Connie Robinson, a teacher at Stockton Riverside College, said: "With less able students it is easy to spot plagiarism as the writing style changes mid-assignment.

"But with more able students it is sometimes necessary for tutors to carry out internet research to identify the source of the plagiarism. This obviously adds to the tutors' workloads."

The problem is exacerbated by the fact that many students do not fully understand the difference between plagiarism and legitimate research.

As a result many teachers believe that the majority of students who engage in plagiarism are acting more out of ignorance that the desire to cheat.

Despite consensus that a robust and well informed policy on plagiarism is critical, over 55 per cent of respondents admitted that their school has no policy to deal with plagiarism.

One solution may be to use Turnitin, a piece of plagiarism-detection software used in most UK universities.

Turnitin is provided via the government-funded Plagiarism Advisory Service, and provides access to a database to cross-check course work.

The software costs between £300 and £400 for 12 months' access.