History teachers are struggling to sell their subject to teenagers as heads direct pupils to "easier" subjects that will deliver better results for the league tables, an academic has claimed.
David Nicholls, professor of history at Manchester Metropolitan university, said an insidious campaign was being waged in schools to dissuade youngsters from taking the subject after key stage 3.
"In some schools the timetable is structured so as to make history unavailable to many students," he said.
Professor Nicholls said young history enthusiasts were being discouraged from taking the subject at key stage 4 and being "directed towards less difficult subjects" by headteachers anxious to secure the best results in league tables.
According to figures from the exam boards, there has been a drop in the numbers taking GCSE and A-level history since 1997.
At GCSE there were 230,125 entries in 1997 compared with 218,565 last year.
At A-level, there were 42,706 entries, with 42,018 in 2003. In 2000, however, the subject declined to 38,533 before an upsurge in popularity.
Professor Nicholls' comments are published in this month's History Today magazine. He urges historians to launch a defence of their subject or risk seeing it disappear from the classroom.
Professor Nicholls said a sequence of events had resulted in the subject's declining popularity in recent years.
The Dearing review of 1996 placed a greater emphasis on the core subjects of English, maths and science and "put paid to any hope that history would be compulsory in the post-14 curriculum".
He said: "England's children are denied automatic access to a history education at an age when their intellectual development is sophisticated enough for them to appreciate its complexities."
He said history teachers had succeeded in engaging children at key stage 3 with a varied and flexible curriculum and often with imaginative and stimulating teaching.
But the constraints of key stage 4 and an emphasis on exam results had led to a more "restricted, knowledge-focused and results-orientated content, undoing much of the previous good work".
Professor Nicholls said the Tomlinson review into 14-19 education offered no guarantees that history could be taught at key stage 4.
The 2012 timescale for implementation could further damage take-up in the subject.
He concluded: "Historians should have no difficulty in running a successful campaign in defence of their discipline.
"If they do not, then the past may have a limited future, to the detriment of the education of the citizens of this country."
Bob Carstairs, assistant general secretary of the Secondary Heads Association, said: "Most heads are in favour of teaching history, but many have issues about the way the curriculum is weighted towards Hitler, Hitler and more Hitler."