England's exams system needs overhauling as top grades "no longer automatically mean top students", the former boss of a major awarding body said on Thursday.
In a new book, Jerry Jarvis calls for students to be given rankings alongside their grades to differentiate between candidates.
Jarvis argues that perhaps the "single great failure" of the exams system is that it has lost the confidence of the public.
He also reveals that the reason why he quit as head of Edexcel was due to concerns that the way exam boards were being asked to mark modular papers would lead to grade inflation.
The book, Cheats, Choices and Dumbing Down, looks at how to navigate England's exams system, and the debate over standards.
It says that the current exams system is "far too complex" and that the way in which GCSEs and A-levels are graded has "undermined confidence in qualifications".
Jarvis warns: "Top grades no longer have the cache that derives from rarity.
"Top grades no longer automatically mean top students.
"It is obvious: if something is commonplace it is no longer special."
More than half of all students who sat exams last summer gained at least a B, the book says, and more than a quarter were awarded an A or A*.
It concludes: "The current system does not effectively discriminate: it does not rank-order the attainment of students.
"Too many candidates attain top grades, undermining the achievement of the very best. The A* is a temporary fix. Does the A** grade appear at some time in the future?"
Jarvis suggests that exam boards could rank students, in addition to awarding grades, with each board having its own list.
"The first student gained an A grade and was ranked at the 83% percentile point and the second at the 73% percentile point," the book says, as an example.
"The first student did better. The percentile point indicates the relative performance of each student compared with his or her peers.
Jarvis told the Press Association that "without a shadow of a doubt" a scheme such as rankings was essential.
"My real concern is that if the public do not believe something's of value, then it isn't of value, no matter how many times you attempt to say it is.
"That's fundamental."
In his book, Jarvis also explains why he chose to quit over his concerns about grade inflation in modular exams.
He says that all exam boards have to abide by a Code of Practice, issued by the exams watchdog Ofqual.
The rules were written to suit single exams, not "modular" or bitesize exams that pupils take throughout their GCSE course, he says.
Jarvis reveals that, in 2009, when modular exams were being introduced, he raised concerns that adding modular exam results together tends to produce a slightly higher overall grade than it would have been in a single exam - known as "grade inflation".
"I was issued with guidance to deal with the problems of adding the results of different modules together," Jarvis writes.
"This meant that I had to award the grades that every student deserved for each module - but then had to apply adjustments to avoid inflation in the overall grade awarded."
Jarvis says he could not accept this situation because he "would no longer be able to claim publicly that the grades awarded reflected the ability of the students that I was responsible for assessing."
As a result, he resigned from his post.
Jarvis told the Press Association: "For me, I was being asked to do an impossible thing. The differences are very small, and you have to understand that I was perhaps nit-picking, but this was a very important thing to me because of where I had come from and what I was trying to do."
Jarvis's call for students to be ranked on their results comes just months after Education Secretary Michael Gove suggested there should be a limit on the number of students who score A* grades at A-level.
Speaking at an Ofqual conference on standards in October, Gove suggested that, in the future, only a certain fixed percentage of students could be awarded an A* at A-level.
This system, known as "norm referencing", was used to grade exams between 1963 and 1987, with around the top 10% awarded an A.
Under the current system, any student who gains an A overall, as well as scoring at least 90% in each of their papers in the second year, achieves an A*.
Gove told the conference: "Could it be the case that while we award As, Bs and Cs entirely on the basis of criterion reached, is there a case for exploring whether or not A*s should be allocated only to a fixed percentage of candidates?
"I would like to see that debate explored and engaged with."
He also suggested that alongside pupils' final A-level grades more information could be produced so it is known "how they are ranked depending on the subject".
Glenys Stacey, chief executive of Ofqual, said: "We have read the book and spoken with Jerry about it. We know that policy makers, experts and others have different views about how qualification grades should be managed, but one thing is clear - they do need to be managed, so that the outcomes, as between one awarding body and another, are fair and that they are comparable year on year.
"This is our job. As to how we do it, we're quite open about that, and open to talking about it. But there will always be different views."
An Edexcel spokesman said: "Jerry Jarvis left Edexcel in 2009 having helped to build our position as one of the most reliable and innovative awarding bodies in the world.
"It's important that we have a debate about how this country can establish world beating standards, so we are seeking teachers', parents' and experts' views on how to improve the system, through our Leading on Standards consultation."