The education minister said he would have been "crucified" by the media and assembly members had he intervened with GCSE grading before the results were announced.
Leighton Andrews AM was giving evidence to the Children and Young People Committee on the GCSE English Language grades of Summer 2012 on 8 November 2012.
Earlier this year, education Minister Leighton Andrews asked the WJEC to
English Language GCSE papers.
This followed a dispute that students had recieved grades which were lower than expected when the results were announced.
Chris Tweedale from the Schools and Young People Group and Cassy Taylor, Head of General Qualifications Regulation, also gave evidence.
Plaid Cymru AM, Simon Thomas, suggested to the minister that he had "let things slip" and allowed the situation to develop "without being proactive enough to nip things in the bud".
Mr Andrews said it would not have been possible for him to intervene in English GCSE exams until after the results were published.
"After I became involved, the question for me was, should I intervene and if so, what would be the implications?" he said.
"If I were to intervene, it would essentially mean I would say the setting of grade boundaries in Wales will be done on a different basis from the setting of grade boundaries in England."
He added that "I think I would've been crucified in the media and indeed by members here" if he had intervened before the results had been announced "because I would've had very little evidence to base that judgement."
Conservative AM Suzy Davies asked him how it had happened that the WJEC had resisted following the English regulator Ofqual's lead in all other subjects except for English.
Ms Taylor explained that the WJEC were the second largest examiner of English in England, whereas in other subjects there they were a "minority" provider.
"As the second largest provider in England, such an important subject, you can understand from Ofqual's point of view why they should be the lead regulator on that," she said.
"The regulator with the most candidates in that subject, will be the lead regulator."
In conclusion, the minister said that there were "lessons to learn" from this year.
"This is a serious moment in three country qualifications.
"I regret to say Ofqual is in an ideological spasm."
The committee also heard evidence relating to child health care from Dr Ruth Hussey, Chief Medical Officer and Dr Heather Payne, Senior Medical Officer, Maternal and Child Health.