Competition between school exam boards leads to pressure which drives down test standards and creates a "race to the bottom," MPs have said.
A report by the all-party Education Select Committee called for "fundamental reform" of the exam system in England and recommended that exam boards be stripped of the right to set their own syllabus and content of test papers.
Instead the committee said there should be a national syllabus for each GCSE and A-level subject, which would be accredited by the exams regulator Ofqual. Each exam board would have to set GCSE and A-levels according to that syllabus.
The committee wants to see an end to schools choosing qualifications which they think may have a higher pass rate to improve their league table statistics. Ofqual would also be given the task of ensuring that exam boards didn't compete by making papers easier, the report said.
Committee chairman, Graham Stuart MP said: "The public have lost confidence in exam standards and this needs to be put right.
"We've got to stop the dumbing down of the courses young people sit and stop exam boards competing on how 'accessible' their syllabuses are."
The committee ruled against creating a single national exam board or single boards for each subject.
Mr Stuart said: "You could move to a single national exam board which would stop the 'race to the bottom' but the change would be disruptive and threaten innovation and cost control.
"Alternatively there are benefits to having one exam board per subject but such "franchising" would create its own difficulties over pricing, tendering and the concentration of expertise."
With the introduction of national syllabuses, "the content of what children learn would be enriched, rigour would be encouraged and both standards and public confidence in them could be restored," said Mr Stuart.
Andrew Hall, chief executive of the AQA exam board, welcomed the report: "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."
Rod Bristow, president of Pearson, which owns the Edexcel exam board said: "It is vital that we address the public perception that competition between awarding organisations leads to downward pressure on standards. Pearson is committed to being a partner in making the changes necessary to enable this."