The Conservatives have promised a radical shake-up of the government agency which has "debauched" exam standards.

In a speech on Thursday, shadow education secretary Tim Collins launched a stinging attack on the performance of the Qualifications and Curriculum Authority (QCA).

The QCA is an independent watchdog tasked with a series of roles including regulating the public examination system and developing the national curriculum.

But Collins said it was failing to safeguard exam standards.

"Rather than pointing the way towards higher standards, the QCA has vigorously led the path downhill," he said.

"The QCA, at least in its present form, is not part of the solution – instead it is the heart of the problem.

"We had hoped to protect standards by modelling an independent QCA on the Bank of England.

"Sadly, to make the present QCA independent would be to reward those who have debauched the currency of exams rather than those who have defended standards.

"Instead we will insist on high standards and a reversal of the dilution in quality."

History lessons

The call for reform came as the party also admitted it had been a "mistake" to make history classes optional from the age of 14.

While it was a Conservative government which permitted that change, Collins said he was prepared to "admit the error" and make the subject compulsory until 16.

"Nothing is more important to the survival of the British nation than an understanding among its young of our shared heritage and the nature of the struggles, foreign and domestic, which have secured our freedoms," said Collins.

"A nation which loses sight of its past cannot long expect to enjoy its future."

Historian Andrew Roberts will lead a new "history curriculum advisory panel" of academic volunteers to draw up a list of approved publications that will be recommended to teachers.