Speaking on a visit to a Cardiff school, the Haverfordwest-born star of Twin Town and Harry Potter and the Deathly Hallows: Part One, said literature and film are vital to learning.
His comments followed those of poet and writer Owen Sheers who has called for GCSE English literature to be reinstated as one of the core subjects in schools.
This summer saw a massive fall in teenagers in Wales taking English literature GCSE. Entries tumbled 44 per cent to 16,835 from 30,100.
Welsh literature also saw a substantial fall in entries but there was a small improvement in results (around one per cent at each of A*, A* to A and A* to C grades).
“We have a body of work in the Welsh language which is up there with the oldest and the incredible literature in Europe,” said bilingual Ifans, at an Into Film Cymru schools event. “And in both languages in Wales, not just in Welsh.
“We should be learning about the great writers of Russia and of the great American novel.
“Denying access to these vast seams of learning, to deny these to a young person is not just neglectful but tantamount to a crime.”
Owen Sheers had described the fall in numbers taking English literature as “very worrying”.
“What is education? It’s not just to prepare children for the world of work, it’s about developing rounded citizens,” he said in the wake of the exam results.
“If (English literature) isn’t a core measure, how do we know that it is being taught in depth, and how do we know that everyone is having the opportunity to access these wonderful texts? We simply don’t. I very much hope it will be reinstated as a core measure.”
Exams regulator Qualifications Wales said that this summer’s fall was partly explained by last year’s significant increase in year 10 entries, which are up from 2,038 to 7,657. But overall there is still a fall in numbers studying English literature to GCSE, and the Welsh government said a review of teaching literature would take place.