Around 100,000 students are believed to have been affected by exam blunders, the Press Association has reported.
The mistakes ranged from impossible questions and printing errors to multiple choice papers without correct answers to choose.
The national regulator of exams and qualifications Ofqual yesterday reassured pupils and parents they were satisfied they had taken enough action to ensure no candidates would be affected by the mistakes. This message was reinforced today by the exam boards responsible. Five of the awarding bodies were involved in the blunders, which were discovered in June.
Mark Dawe, chief executive of the OCR, said: "We regret those mistakes and we are very sorry about them.
"We can reassure candidates significant work has been undertaken to ensure they get the grades they deserve."
Christine Blower condemned the errors. The general secretary of the National Union of Teachers, who blogged for Huffington Post UK this morning, said: "The spate of errors in this year's examinations was inexcusable and it is vital that any appeals arising are dealt with as a matter of urgency."
In its first intervention since the mistakes came to light, the Department for Education said the errors were "completely unacceptable".
Secretary of State for Education Michael Gove also slammed the exam boards shortly after the mistakes were revealed. A spokesman for Gove said in June: "The Secretary of State is angry about these and other errors. He has said repeatedly that the exam system is discredited and action must be taken."
Students who were affected by the mistakes are expected to receive priority treatment through clearing if they have narrowly missed out on a university place.
Ofqual are offering advice for students after they have received their grades via their helpline on 0808 100 8000.