Exam board Pearson is to be questioned by MPs about why many students are still missing grades.
Chairman of the education select committee Robert Halfon MP has suggested if issues are not resolved, exam boards should issue affected schools with a refund.
Pearson said some 5,700 students were awaiting BTec (Business and Technology Education Council) results last Thursday, when pupils started receiving their GCSE grades.
The exam board said that changes made this year in order to take into account disruption to teaching and learning during the pandemic, had added more complexity to the process.
In an interview with BBC Radio 4's Today programme, Halfon said he had met with Pearson and told them the delays were "unacceptable".
He said: "They knew this problem from early July, because there were delays from some school results. There should be no reason for this delay.
"We're going to call Ofqual and these organisations - Pearson and others - to our education select committee and ask questions to make sure we don't just have this again next year."
An Ofqual spokeswoman told the BBC: "We will examine all relevant information to better understand what has happened and what needs to change to ensure that students are protected.
"Should we find the awarding organisations have been at fault, we will consider what action, including possible regulatory action, is appropriate."
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