Headteachers who are paranoid about Ofsted are putting pressure on teachers to produce "excessively detailed" and unnecessary lesson plans, the ATL conference will hear next week.
Teachers are calling for heads who compel them to create elaborate plans to explain their actions to union leaders.
Ofsted, which is due to contribute to a review of lesson planning guidance, said there was currently "no expectation" that teachers should supply inspectors with a lesson plan.
But the inspectorate is interested in "how planning is used to support learning", leaving open the prospect of inspectors asking to see plans.
David Ambler, executive member for Birmingham at the ATL, will tell the conference that the practice cannot continue.
He told The TES: "I can understand that if a school is in special measures then detailed planning might help get them out of a category, but we have had calls about excessive demands from teachers in schools that are not in categories.
"For teachers who are delivering 20 lessons a week, if you're teaching a similar lesson to different groups across a year it might be okay, but in a relatively small school that's an awful lot of lesson planning that is no longer required."
Lesson planning is just one topic for discussion at this year's ATL conference. Debates will also he held on whether Ofsted and the controversial "Licence to Teach" should be abolished. There will also be calls for improvements to paternity pay, and the introduction of sabbaticals for teachers who have served for more than seven years.