The union wants all course work to be completed in school
A planned shake-up in Scotland's exam system could lead to more pupils cheating, a teaching union has warned.
The Scottish Secondary Teachers' Association (SSTA) believes a new emphasis on marking work completed outside the exam hall could be abused.
It fears children could be given help to complete the work by parents, private tutors or the internet.
A Scottish Government spokeswoman said: "This is a consultation and we welcome ideas about the proposals."
In a consultation paper, ministers said exams would not disappear altogether but teachers would award their pupils grades for coursework rather than give them a basic pass or fail competence test as they do now.
David Eaglesham, general secretary of the SSTA, told BBC Scotland he was in favour of the principle.
But he said it was important all coursework was completed in the classroom, where pupils could be fully supervised by teachers.
Mr Eaglesham added: "We would welcome the general principle that more coursework be assessed as part of the overall examination system.
"The difficulty we have is that if the work that is done is a kind of project-based work where much of it is being done outside of the school, then there is a potential difficulty in verifying that the work is in fact that of the pupils themselves.
"We would prefer to see any internal assessment being done literally inside the school so that the work is being verified by teachers and they can attest to the fact it is the work of the pupils.
"There are a range of assessment techniques which can be used to make that happen."
The Scottish Government announced earlier this year that the Standard Grade and Intermediate exam system was to be replaced with a new general qualification for pupils.
Compulsory qualifications to test numeracy and literacy will also be introduced, but Higher exams will remain.
The new certificates will be tested in fourth year through a mixture of an exam and assessment of general work through the year.
The government spokeswoman added: "The consultation paper clearly states that external exams will be retained at all levels where they are currently used for certification.
"However, we believe that there may be scope for making better use of different types of assessment alongside external exams depending upon the individual nature of each course.
"Different kinds of assessment such as projects, performances and practical tasks are already features of Scottish education and we want to explore this issue further."