Examiners suspended following claims that exam boards were giving teachers unfair advice have told MPs they regret their secretly-recorded comments.
But they argued it did not mean that the system was inherently flawed.
"I am only human and everyone makes mistakes," said Steph Warren, who was recorded at an Edexcel seminar saying "you don't have to teach a lot".
Examiners from the WJEC board denied the suggestion that exam bodies were chasing "market share".
The House of Commons education select committee is investigating reports in the Daily Telegraph that appeared to show exam board seminars giving teachers inside information on exams.
Paul Evans, who had been recorded appearing to say that there was "cheating", told MPs that his use of the word had been "inappropriate".
But he argued that in practice the integrity and confidentiality of exams had not been compromised.
Ms Warren also told MPs that her recorded comments did not represent her considered views on the relative difficulties of exams.
While these staff expressed their regrets at the recorded comments - senior figures in their organisations have rebutted any criticism when MPs raised questions about the exam system.
Mark Dawe, chief executive of the OCR board, told MPs that this was one of the most transparent exam systems in the world.
He denied any suggestion of a widespread problem that needed to be addressed.
The exam board heads also told MPs that seminars and events giving advice to teachers were run at a loss and were not money-making ventures.
MPs were told that evidence of an underlying problem with the system was "non-existent".
Asked by MPs about how schools chose between exam boards, Rod Bristow, representing Edexcel, said it was "price, service and support".
Mr Bristow also went further in conceding the need for change, saying: "I think the events that we have seen mean that we do need to strengthen the systems and processes."
He also promised that if there were reforms that "nothing should be off the table".
Glenys Stacey, chief executive of the Ofqual exam regulator, also faced the committee - and described the Daily Telegraph's investigation as an "excellent job".
But when pressed by MPs about the perception of differences in difficulty between courses offered by exam boards, she was not drawn into identifying such differences.
MPs also raised questions about whether qualifications were robust enough for employers and universities - and whether the pressure on schools from league tables was distorting the exam process.
But Ms Stacey called for "reflection" before any major changes were made to the system.
Committee chairman Graham Stuart, following her guarded responses, prompted laughter when he told her: "You should be in politics."
Mr Stuart, in a statement before the hearing, had said: "We are already conducting an inquiry into exam boards, looking into conflicts of interest and the need for reform.
"The Telegraph has carried out a public service in exposing the actions of some very senior examiners. The stories are shocking and suggest there may be a need for radical changes."
Brian Lightman, leader of the ASCL head teachers' union, has attacked the "constant tinkering" with the exam system, warning that this is undermining its reliability.
"It creates chaos for teachers, students and exam boards, all of whom were just getting to grips with the last set of changes."
The exam regulator confirmed on Wednesday the next set of changes, as schools will be told to move away from the current modular GCSE system.
In response to the newspaper allegations, John Dunford, chair of the Chartered Institute of Educational Assessors, called for all markers and examiners to be "independently trained".
Education Secretary Michael Gove has also announced an inquiry into the claims about exam boards.