More than 45,000 grades from this summer's exams have been changed after schools challenged them - an increase of 15 per cent.
The number of inquiries questioning GCSE and A-level grades however rose even more sharply, up by 48% to 450,500, according to exam watchdog Ofqual.
There were warnings that mistakes in marking could mean that young people missed out on university places or being able to stay on to take A-levels.
About one in every 33 scripts marked this year resulted in an inquiry about marking or grades.
This meant 45,500 grades have been corrected - up by 15% compared with the results of summer 2013. It represents a much bigger increase over the last few years - about 50% more grade changes than 2011.
"Every such change has a big impact on the individuals affected," said education minister Nick Gibb.
"There is a growing lack of confidence in the exam system," said head teachers' leader Brian Lightman.