Examiners are being allowed to mark this year's Sats tests despite performing so badly that they would have been struck off in previous years, The TES has been told.
Senior markers have said that, in some subjects, all examiners they knew were allowed to pass an initial vetting process this week, no matter how accurate their marking.
One marker leading a team of nine for key stage 3 maths marking, said: "Many people who should not be marking, are. There are obvious consequences for the quality of the marked scripts that will be returned to schools."
The National Assessment Agency, which oversees marking, says the vetting process has changed this year, and that examiners who pass initially will face tougher checks later during the marking process.
The comments will intensify pressure on ETS Europe, the not-for-profit company that is running national test marking for the first time this year.
Last week, The TES revealed that hundreds of examiners had complained about the company's organisation of marking, particularly training events and contracts.
The maths team leader, who cannot be named because all markers have signed confidentiality clauses, said: "The lack of quality control worries me even more than the awful admin."
Markers are vetted through an on-screen "standardisation" process that involves marking six pupils' sample scripts. Their work is then compared automatically with that of a senior colleague.
A software problem last week meant that virtually all those who were vetted for KS3 English failed. The glitch was fixed after several days. But markers said the system had now gone to the other extreme.
One team leader said that everyone he knew who had taken the KS3 maths standardisation test had passed.
Initially, he said, team leaders were told that markers would have to complete another check if their sample results differed from those of the senior marker by more than 12 marks. But this requirement was dropped. Some markers, he said, had passed despite being out by more than 50 marks.
A KS3 science team leader said: "All my team have passed, regardless. I have grave doubts over the quality of marking we can expect."
An experienced KS3 English teacher said that examiners were not being given feedback after their standardisation tests as to where they had marked too harshly or too leniently.
Andy Latham, vice-president of ETS, said that more than 90 per cent of markers had passed the initial standardisation process for KS3 tests in English, maths and science.
Markers have to go through further benchmarking checks for every 80 papers they mark, he said, and these would be more stringent than the standardisation checks.
ETS argued that its new checking system would ensure marking was controlled more tightly than before.
Markers have continued to bombard The TES online staffroom this week with complaints about the marking process.
A marker's experience, page 12
Letters, page 30.