Boris Johnson is under pressure to intervene in the exam crisis in England, amid growing anger among pupils and teachers.
Labour leader Sir Keir Starmer called on the Prime Minister to take "personal responsibility" for fixing the issue, accusing him of having been "invisible" throughout the turmoil.
Almost 40% of all A-level grades in England were marked down as a result of the standardisation process, and ministers are now braced for another backlash when the GCSE results – which are moderated using the same algorithm – are released on Thursday.
Receive newsletters with the latest news, sport and what's on updates from the Liverpool ECHO by signing up here.
The Conservative former education secretary Lord Baker of Dorking has urged ministers to delay the publication of GCSE results, due this week, until the problems with A-levels had been resolved.
The Department for Education (DfE) has said it is continuing to work with the regulator Ofqual to build as much "fairness into the appeals process as possible" to help what it described as the "most difficult cases".
* Do you think the GCSE results should be delayed? Tell us in the comments
While there is talk of GCSE results being delayed, shadow education secretary Kate Green said that "options have to be kept on the table".
Keep up to date with local news in your area by adding your postcode below
Asked whether GCSE results should be delayed, Ms Green told BBC Breakfast: "I certainly don't think that delay is an ideal outcome either for students or for those education institutions.
"We did say last week that the Government should use teacher-assessed grades in respect of A-level students, underpin that with an appeals system in case a student feels that their teacher-assessed grade isn't correct – but now, of course, we don't know what kind of appeals system students are going to be relying on.
"It is a completely unsatisfactory situation for these A-level students still days later after the results came out last Thursday."