Education Secretary Christine Choi on Saturday said a new set of guidelines on teachers' professional conduct will clearly spell out some red lines that cannot be crossed.

She said officials had finished drafting the guidelines and that they would be released before the end of the year.

Choi explained that the guidelines would set out clear principles and limits on teachers' behaviour, illustrated by examples.

"We hope to move with the times, respond to society's expectations for teachers and uphold teachers' professionalism," she said.

"The guidelines will state clearly what teachers should and should not do, as well as some serious, unacceptable red lines."

She said she hopes the new guidelines will give school operators and teachers a better understanding of the high standards of conduct expected of the teaching profession.