League tables lower standards, are unfair, vague, imprecise, have "serious structural problems", damage pupils and need to be reformed, according to two exam boards.
Such strong criticism from Cambridge Assessment and Edexcel - two of the three main boards - adds to pressure on ministers to reform a regime which many argue creates unacceptable distortions in schools.
Last week the Government's experts group on assessment recommended replacing league tables with school report cards "as soon as is practically possible".
Cambridge Assessment argues that responsibility for compiling and deciding what goes in the tables should be transferred from the Government to Ofqual, the new exams qualifications regulator.
In a submission to the Commons schools select committee, the parent company of the OCR board warns that the tables "exert a strong downwards pull" on exam standards. Schools switch to qualifications with "lesser educational merit" where it is easier to achieve high grades and boost schools' league table positions, the board says.
It adds: "It is not at all clear that performance tables have impacted beneficially on interaction in the classroom; indeed there is evidence that more superficial learning approaches have been adopted in a misguided attempt to maximise examination performance."
Simon Lebus, chief executive of Cambridge Assessment, told MPs there was an "absurdity" in the tables. In trying to "create artificial parity" between skills-based IT and general academic qualifications, they had created an incentive for schools to behave in a particular way.
He did not say whether he meant that schools were flocking to the OCR's own national level 2 in ICT, which is worth four good GCSEs in the tables, even though it typically takes only half the time to teach. And, according to National Strategies consultants, the standards required for a pass in this exam are equivalent to those expected of an average 11-year-old.
Jerry Jarvis, Edexcel's managing director, told MPs that he thought Ofqual should look at the equivalence of different subjects in the league tables. His board criticises the tables for failing to differentiate between schools according to their intake, funding and value-added scores. Edexcel says they distort demand for places in particular schools, with "damaging consequences for learners, communities and social cohesion".
Mr Lebus said: "I think that the current system does not work very well. It is vague, imprecise and gives peculiar results that are not felt to be fair by a number of schools that are taking part."
But the tables are unlikely to disappear. Ed Balls, the Schools Secretary, told Parliament last week that banning them was "simply not an option". The final draft of the experts group report watered down its initial recommendation on report cards, saying they should replace tables as the "focus of public accountability for schools".