Clayton Heycock, secretary of the Welsh Joint Education Committee which provides most of the exams for Welsh schools, said: "The competitive ethos is totally inappropriate in education. There is a danger that you may lower your standards to attract more entries."
Such fears drove the School Curriculum and Assessment Authority earlier this year to introduce sweeping measures to maintain standards. These include a mandatory code of practice.
SCAA is also scrutinising this summer's GCSE results and the number of syllabuses offered by exam boards is being streamlined so that there will be a dozen rather than the current 40. This should make it easier for SCAA to compare standards across rival boards.
SCAA's concern that some exam boards' were giving more and higher grades was heightened last summer by a survey of maths and science GCSEs which found that grade boundaries had been changed to increase the number of passes. League tables have made exam grades a vital issue for secondary schools.
Tony Millns, assistant chief executive at SCAA, said: "Evidence from our inquiry last year indicated the commercial pressure on examining boards. This is a fraught area and we shall be watching this year's exams closely for evidence that standards are being maintained."
The WJEC believes the answer is to have a regional approach with each board serving one area. Mr Heycock said his committee was selling itself in England and 400 schools and colleges now offered its exams. But he would rather his staff devoted more time to honing each syllabus than touring the UK on sales missions.
The WJEC fears were rejected by John Day, joint secretary of the Southern Examining Group, who believes competition between exam bodies will affect only service and support for schools.
"I don't think competition will ever relate to standards of examining, " he said. "I can't believe that any examining board would depress standards to attract more schools. It wouldn't be a sensible thing to do. There is a good amount of regulating now."
John Sutton, general secretary of the Secondary Heads Association, believes that monitoring by SCAA would quickly detect lower standards. "What I suspect is that the particular style of a paper suits the school's teaching rather better than another."
He added: "There is room for competition, but in such areas as making themselves more user friendly and more helpful to schools, particularly in areas like timetabling. They could also compete in terms of fees."
John Bangs, head of education at the National Union of Teachers, believes the measures implemented by SCAA will dispel any suspicion of inequality in awards. "It is very hard to say if this has gone on in the past but any misapprehensions can now have no basis with the new sanctions and controls. "