There are warnings of a shortage of history teachers in England - weeks after the subject was made central to plans to promote social cohesion.
History stops being compulsory after age 14
History teacher training places have been cut by 40% since 2004, according to data obtained by Liberal Democrat education spokeswoman Sarah Teather.
The Teacher Training and Development Agency said the fall reflected demand.
But Ms Teather said many schools were struggling to fill history posts and that a third of teachers were over 50.
The figures emerged shortly after Education Secretary Alan Johnson said he wanted to use teaching about slavery and the legacy of the British Empire as part of citizenship lessons.
They show that whereas in 2003-4 1,024 training places were allocated for history teachers in England and Wales, in 2007-8 this will fall to 583.
"It's so short-sighted to write off history as a low priority subject. In the next decade we are going to see the majority of history teachers hit retirement age," Ms Teather said.
"Without a real effort to get young, dynamic graduates into the classroom there's a risk of a whole generation of pupils missing out on a core plank of their education."
The Lib Dems argue the problem is likely to become particularly severe in urban areas, where far fewer pupils are taking the subject at GCSE compared with more affluent, rural and suburban areas.
Meanwhile, the number of history graduates becoming secondary school teachers has fallen by nearly a fifth since 1998-09, the figures in a Parliamentary written answer show.
Ms Teather added: "The government wants to use British history to teach young people about British values and traditions, but plans to promote social cohesion through the curriculum will remain a pipe dream when so many pupils aren't being taught history at all.
"This government's obsession with targets and testing at the expense of everything else mean that subjects like history which can teach pupils a wealth of things about national identity, politics and culture are going to the wall."
The concerns were reflected by the Historical Association, which represents history teachers.
The chair of its secondary committee, Heather Scott, said shortages were likely after training places had been cut.
"It is a cause for concern because it is ever increasingly apparent that it is important that students are taught by history specialists who understand what they are doing.
"We are anxious about it."
She added: "In general in teaching there is a huge watershed going to happen in the next 10 years as a huge amount of teachers in secondary schools are aged over 50."
The TDA said the fall in history teacher training places mirrored its campaign to increase the number of secondary maths and science teachers which were in particular demand by schools.
Last year there were 2,499 places allocated for maths and 3,375 for science and next year there are 2,534 places allocated for maths and 3,400 for science, the TDA said.