Teenagers have been let down by an exam system that is abused by teachers who are under intense pressure to achieve good grades, Ofqual has warned.

Teachers in some of England's secondary schools were guilty of "significantly" over-marking pupils' GCSE English work this summer in order to boost results, according to chief regulator Glenys Stacey.

In a new report into the GCSE English fiasco, Ms Stacey said that it is hard for teachers to maintain their integrity, when they believe that others are abusing the system.

"We have been shocked by what we have found. Children have been let down. That won't do," Ms Stacey said.

"It's clear that children are increasingly spending too much time jumping through hoops rather than learning the real skills they need in life.

"Teachers feel under enormous pressure in English, more than in any other subject, and we have seen that too often, this is pushing them to the limit."