Thousands of pupils are now getting only two years worth of teaching in the subject at secondary level, instead of the expected three, it was claimed.

Ed Balls, the Schools Secretary, admitted that teachers should have the “flexibility” to cut the amount of time devoted to certain subjects.

But David Laws, the Liberal Democrat children’s spokesman, said the move was a "disgrace".

"Ed Balls is giving the green light to schools to allow pupils to dump crucial subjects such as history as early as age 13," he said.

"Pupils already have the freedom to stop studying key subjects such as modern languages and history at age 14 - and Ed Balls' latest move is a step too far. The teaching of history is a crucial part of providing a broad and balanced curriculum which informs young people about the World in which they live.

"Dropping this subject at age 13 is bound to leave many young people ignorant about key events and issues in British and World history.