The changes to A and AS-levels in England are so confusing the Department for Education should write to every school to explain them, says shadow education secretary Tristram Hunt.
From next year, A-levels will be separated from AS-levels.
But some universities still want pupils to study AS-levels – and Cambridge has asked schools to carry on with them.
A Department for Education spokeswoman said the changes would remove an “unnecessary burden” on pupils.
Brian Lightman of the Association of School and College Leaders said “politics is getting in the way”, with secondary schools facing “confusion and uncertainty” over planning for exams.
Mr Hunt, in a speech at the Association of Colleges’ conference, will accuse the government of “failing in its duty” to keep parents and pupils “properly informed”.
He wants the permanent secretary at the Department for Education to write to the heads of schools and colleges explaining the changes to exams and to tackle “widespread confusion”.
Uncertainty about AS-level changes is “the biggest real-time issue in secondary schools”, says Mr Hunt.
He also wants the letter to explain the alternative arrangements that would be in place if Labour entered office after next year’s general election.