Schools and colleges have been told not to issue BTEC results to students on Thursday following a last-minute U-turn on grading.
On Wednesday – with less than 24 hours to go until results day – exam board Pearson asked schools and colleges not to publish level 1 and 2 results in the vocational qualifications to give them more time to recalculate the grades.
It follows the announcement that GCSE and A-level students would this year be able to receive grades based on their teachers' estimates.
BTEC students' grades were not included in the original announcement, but now Pearson has said it will be regrading BTECs awarded last week – as well the grades that were due to be released tomorrow.
It comes after education unions and the Labour Party called on the Government to provide clarity on why BTEC students had been left out of Monday's grading U-turn.
A spokeswoman for Pearson, the provider of BTECs, said: "Following Ofqual's announcement that A-level and GCSE students are to receive centre-assessed grades, we will be applying the same principles for students receiving BTEC results this summer.
"We will be regrading BTECs to address concerns about unfairness in relation to A-levels and GCSEs and ensure no BTEC student is disadvantaged."
She added: "We know this could cause additional uncertainty for students and we are sorry about this.
"Our priority is to ensure fair outcomes for BTEC students and we will work around the clock to provide revised grades as soon as we can."
Kate Green, Labour's shadow education secretary, said: "This latest chaos is totally unacceptable.
"For some young people to find out less than a day in advance that they will not be receiving their grades tomorrow is utterly disgraceful.
"It's appalling that thousands of young people should face further confusion and uncertainty because of the Government's incompetence.
"This repeated chaos is simply no way to run a country. The Government must urgently set a clear deadline for every young person to receive their grades."
On Tuesday, exams regulator Ofqual said its moderation algorithm used in A-levels and GCSEs was not used in the majority of vocational and technical qualifications (VTQ) – including BTECs.
But in a statement on Wednesday night – just hours before results were due to be published – England's exams watchdog said some exam boards, including OCR and Pearson, will "need more time" to recalculate results.
It said: "OCR have said that their Cambridge National results will issue next week.
"Pearson, which initially did not think there would need to be significant changes made, has now decided to revise its arrangements to ensure that students' qualification-level results better reflect the unit-level results that students have already secured through internally assessed units."
Ofqual added: "Everyone is working as quickly as possible to confirm results as soon as possible, recognising the impact that delays are having on schools, colleges and students.
"No learner's result will go down as a consequence of regrading."
David Hughes, chief executive of the Association of Colleges (AoC), said: "The timing is worrying, because thousands of students were due to get their results in the morning and others have already got results which we know will not go down, but which might improve.
"So it is vital for students that this is sorted in days rather than weeks so that students have the chance to celebrate and to plan their next steps. It is a stressful time and this delay will extend the uncertainties."
He added: "Those students wanting to move onto further or higher education will be most worried about losing out on places.
"We are in close communication with DfE, Ofqual and Pearson to particularly make sure that BTEC students applying for universities can still be treated fairly."