Teachers are being asked to help stamp out cheating in coursework and exams by signing up to a tough set of ethical standards.

The code came into effect yesterday, and will affect all 10,000 teachers and examiners who are members of the Chartered Institute of Educational Assessors (CIEA). Many more teachers are expected to sign up to the code in future as curriculum changes give them a greater role in assessment.

Isabel Nisbet, acting chief executive of the new exams watchdog Ofqual, said a code was needed to re-earn the trust of the public.

Teachers can be tempted to get the best scores for their pupils by any means necessary, Ms Nisbet said. And the introduction of diplomas, which will put more responsibility on teachers to grade work, will create further “challenges”.

The code of practice will make clear how members of the institute should conduct themselves. It will be backed up by disciplinary powers that could see members expelled if they fail to meet its standards.

Graham Herbert, CIEA deputy head, said that helping to prevent cheating would be one of the positive effects of the code, which had broader aims to promote good practice in marking.

Ms Nisbet, who spoke to members of the CIEA last week, said England should follow America in having a clear code of conduct.

Teachers should speak out against low standards and report colleagues if they are aware of malpractice. “The whole area of internal assessment is difficult. The vast majority of teachers and assessors are on the side of the angels in all of this. They will be blowing the trumpet for best practice.” Ms Nisbet told The TES.

Ofqual, which only came into operation last month, was established to uphold the standards of exams and qualifications.

Its introduction followed claims that pupils were cheating in coursework after receiving too much help from parents and teachers, or cribbing unfairly from the internet.

A number of teachers have admitted telling their pupils what to write in coursework because of the pressure to get good results.

Work-related diplomas, being introduced from this September, will put added responsibility on teachers to mark their pupils’ work internally. But unsupervised course- work is being dropped from most academic GCSE subjects next year to be replaced by ‘controlled assessment’, which teachers will set for pupils in supervised conditions and then grade.

Mary Bousted, general secretary of the Association of Teachers and Lecturers, questioned the impact of a new code of conduct.

“Teachers are already clear on what is ethical and unethical behaviour,” she said.

“The accountability framework, with league tables and Ofsted, puts teachers under pressure. We need to look at what drives conduct that we don’t want to see.”

Alan Smithers, professor of education at Buckingham University, said: “Teachers are very principled and work to their best instincts. But the rules of the game are set up in a way that encourages the kind of behaviour that a code of conduct might frown upon.”