The country's largest teaching union has said there is "an artificial crisis where none exists" over GSCEs.
The NASUWT said the government has a "pre-determined political agenda" that could undermine the exams system.
Commenting on today's report by the Education Select Committee into the administration of examinations for 15-19 year-olds in England, Chris Keates, general secretary of the NASUWT, said:
"This is a critical debate but it needs to be conducted on the basis of facts, not as a response to assertion and rhetoric about allegedly declining standards and highly dubious claims about the ‘dumbing down’ of qualifications.
"If public confidence in the examination system has been undermined, this is as a result of ill-informed, ideologically-driven public debate, seemingly deliberately fuelled by misleading and inaccurate ministerial comments about a lack of rigour and stretch in the qualification system. Such comments are noteworthy only for their lack of substantiating evidence.
"There may well be a case for revising the current system of awarding bodies. However, this should not be driven by the notion that awarding bodies compete with each other for business on the basis of the ease with which qualifications can be passed. The Government’s own evidence has shown such claims to be mythical."
The largest of the three English exam boards, AQA, has welcomed the report as "thoughtful and rigourous".
Andrew Hall, chief executive of AQA, which awards 49% of GCSEs in England, said:
"AQA has never competed by lowering exam standards, although I accept this may have been the case elsewhere in the market in the past. We have been pressing for stronger regulation of standards between awarding bodies for some time and have been pleased to see that the regulator has addressed many of our concerns over the last year.
"However, we recognise that it is important to restore public confidence in the system. We want everyone to be clear what level of knowledge, skills and understanding a qualification represents to ensure that students’ achievements are properly recognised."
Mr Hall said the Committee’s recommendation of a single syllabus for key subjects and the imminent consultation about government proposals "clearly sign-post that significant change to the exam system is coming".
He added: "Whatever the final decisions, we would urge policy-makers to ensure that the right measures are put in place to protect students and maintain standards in a meaningful and credible way."