An ITV News investigation has also found the exam board WJEC questioning a pledge that pupils will end up with fair overall grades.
Emails released by Welsh Government show that the exam board warned that a regrade of GCSE English papers would affect integrity
Education Minister Leighton Andrews has told AMs he stands by his decision to order a regrade for this year's English Language GCSEs
Unions NAHT Cymru & ASCL Cymru have written a joint letter to WJEC, asking it to waive fees for re-sitting GCSE English Language units this summer.
"We have to report that our members are extremely dissatisfied with the position that their staff, pupils and parents now find themselves in" said the letter.
"This is a highly unacceptable state of affairs as young people begin to prepare in earnest for the challenges of the array of summer examinations."
The National Union of Teachers says it has also asked WJEC to waive fees to re-sits this summer.
Exam board WJEC says it welcomes the findings of the Welsh Government's review into January's GCSE English Language results, and said the immediate actions identified are being implemented.
– Gareth Pierce, WJEC’s Chief Executive
WJEC sympathises with candidates and teachers who have been affected by the unexpected outcomes for these January series units, but hope that this review provides the context for these outcomes and that the steps now being put in place will ensure confidence in arrangements for the summer series and for subsequent years.
The Association of School and College Leaders (ASCL) Cymru says schools and parents should not be charged for English GCSE re-sits after January's poor results.
– Robin Hughes, ASCL Cymru Secretary
The immediate concern must be the fact that we have students who have received grades that do not reflect their abilities and which are far below expectation.
Given that schools and teachers have been exonerated, ASCL insists that schools should not have to pay for these re-sits, at great cost to their budgets. It is also unfair for parents to be asked to pay directly for them.
The minister has an opportunity to show leadership and support ASCL’s call that the cost of these re-sits should not be placed upon schools and parents.
The union added that the new regulator, Qualifications Wales, should consider "whether any grades at all should be given for January entries".
The Shadow Minister for Education in Wales has described a Welsh Government review into January's English GCSE grades as 'little short of a whitewash'.
– Angela Burns AM, Shadow Minister for Education
After a month of waiting for answers, this report fails to adequately explain to students, teachers and lecturers why exam results were so much lower than predicted.
Students, teachers and parents remain in the dark about how many exam papers will be remarked and how their overall grades will be affected.
The Welsh Government must rapidly learn the lessons of this fiasco and consider delaying the introduction of its five other Wales-only GCSEs to prevent any other young people going through this stressful and distressing ordeal.
The review concluded there was 'no one single aspect' that contributed to the lower grades and said there was no evidence to suggest that WJEC did not follow correct procedures.
Following its review into claims of low January English Language GCSE grades, the Welsh Government has made a number of immediate recommendations.
The review found 'no one single aspect' contributed and that there is 'no evidence to suggest that WJEC did not follow the correct procedures' - but said the recommendations would 'address the concerns of learners, parents and practitioners' and 'help to build confidence' across the system.
1 Copies or samples of papers must returned to schools as soon as possible so teachers can begin to look at how they have been marked in relation to the marking scheme.
2 WJEC is to extend registration deadline to allow schools to consider in more detail which pupils should be entered for re-sit in June.
3 Further materials should be produced before the Easter break to explain how the mark schemes will be applied to students' work, in order to increase transparency.
4 Training and new exemplar materials should be made available online before the Easter break, including sample papers. Schools should explain to teachers how marks are given and what they need to do to gain these marks.
5 Free additional sessions run by the WJEC before summer exams must ensure that advice given to schools is consistent with that provided in the examiner's report - and across the board.
6 January units need to be on the online review section of the website immediately.
An urgent review into claims thousands of GCSE pupils in Wales received unexpectedly low grades in their January English Language papers has concluded 'no one single aspect' contributed.
– Welsh Government: January 2014 GCSE English Language unit results fact-finding exercise
It appears that our sample schools were generally prepared for the new specification and the revised weighting for SSPS [sentence structure, punctuation and spelling]. Indications are that schemes of work were amended and predicted grades were modelled on the new specification. Generally the examination papers matched teachers’ expectations of the new specification and there were few surprises for teachers or pupils. There is no evidence to suggest that WJEC did not follow the correct procedures at all times.
The review did, however, identify a number of themes - including changes in entry patterns; late change to specification; increased weighting on accuracy, sentence structure, punctuation and spelling; insufficient quality and quantity of support materials; and a 'difficult to navigate' WJEC website.
It added: "The drop from 23.6% C grades for Unit 1 Foundation Tier in January 2013 to 4.6% in January 2014 should certainly have focused attention. The fact that lower outcomes were communicated to Welsh Government on the date of publication is a concern."
The Welsh Government is today due to publish the findings of its urgent inquiry into claims thousands of GCSE pupils in Wales got unexpectedly low grades in new English language papers they sat in January.
After dozens of headteachers complained of shock low results at the beginning of the month, Education Minister Huw Lewis launched a "rapid fact-finding exercise... to understand what are the key issues underlying the results."
22,516 pupils sat at least one unit of their English language GCSE in January.
The exams were the first to be sat under a new, more rigorous, English language qualification for Wales only, after a row over the regrade of papers in 2012.
Figures from exam board WJEC show 48 out of 292 centres (16.4 per cent) entering pupils in January saw an average fall of more than one grade compared to last year.
For Unit 1, at Foundation Tier, the proportion of pupils awarded a C grade fell from 23 per cent to 5 per cent.
WJEC held its own review of marking, but said that - aside from one inconsistent examiner - the vast majority of papers were marked "correctly and accurately in line with the mark scheme".
WJEC has sent a letter to schools offering to show them papers from January's GCSE English Language exam for 10% of pupils free of charge.
A small number of papers are being re-marked, because of inconsistency by one examiner - but WJEC said the vast majority were marked correctly.
The board said the move would be an opportunity to "illustrate" marks and grades awarded.
Welsh exam board the WJEC has defended its marking of January's new GCSE English language exams - after thousands of pupils got lower grades than they'd expected.
A small number of papers are being remarked, because of inconsistency by one examiner - but the WJEC said the vast majority were marked correctly.
Opposition parties in the Senedd have this afternoon argued that there are still no anwers for pupils, parents or teachers over what's behind the shock low grades.
We have been taking a closer look at January's exam papers, to try to find out.