Education Secretary Michael Gove is to appear before MPs as the row over GCSE English grades descended into farce.
A Welsh exam board has called on regulators in the principality and England to agree on a "common view" on how to resolve the crisis.
The WJEC exam board - previously the Welsh Joint Education Committee - made the plea after Welsh education minister Leighton Andrews ordered it to re-award its English language GCSE following a Welsh Government review.
But with the regulator in England, Ofqual, standing firm on the issue, WJEC, which sets GCSEs in both nations, is in the unusual position of having to regrade exam papers sat by pupils on one side of the border but not the other.
Mr Gove has refused to intervene despite warning that GCSEs are "unfit for purpose". Ministers should not "meddle" in decisions made by Ofqual, which is an independent regulator, he said.
Meanwhile, a teaching union suggested that at least 143 secondary schools are at risk of being labelled as failing and forced to turn into academies after they were affected by the row.
And appearing before the Commons education select committee on Tuesday, Ofqual chief Glenys Stacey admitted that she would have forced Edexcel, one of England's biggest exam boards, to alter its GCSE English boundaries to avoid grade inflation.
WJEC said in a statement: "In the summer we acted on joint instructions from regulators to adjust our GCSE English language awards downwards at Grade C, in order to ensure comparable outcomes. We now find one regulator confirming that the decision made was correct, and another asking us to regrade, reversing the previous joint decision. As an urgent next step, we have asked the regulators to explore the possibility of agreeing a common view so that we can act to remove the uncertainty for schools and colleges in England and Wales, and ensure a coherent and rational way forward for all our candidates."
It came after Mr Leighton turned a request that WJEC regrade the affected GCSE English exam papers into an order that they do so. He said: "It is not right hundreds of our learners should have to live with the consequences of having been awarded what, in all likelihood, is the wrong GCSE grade.
"We are fortunate in Wales that we have a regulatory system which allows swift resolution of injustice. We have acted to protect the interests of students in Wales, by issuing the direction to the WJEC."
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