Controversy over the exam system, which used computerised “standardisation” this year in the wake of the pandemic, spiralled when ministers bolted on an appeal route using mock results.
Many A-level students were left distraught after some 280,000 entries were downgraded from teacher assessments amid cancelled exams.
Andy Burnham said “dismay” had been expressed by college principals and headteachers in his area and said students have experienced a “significant downgrading” of marks compared to previous years.
“But worse, I heard stories of young people, who have already suffered a terrible year, having yet another injustice done to them,” he said.
“One college head spoke of 1,600 students being marked down and just 10 being marked up. Another spoke of young people being given a fail for exams they didn’t even have the opportunity to sit.”
Mr Burnham said he believes the system used to mark A-levels is “inherently biased” against larger educational institutions.
“Given that a higher proportion of students from Greater Manchester attend such institutions than in other parts of the country, I am concerned that the marking system has been unfairly discriminatory against young people here, in part due to the institutions they attend,” he said.
“I am considering all options to challenge this unfair process, including a legal challenge against the Office of Qualifications and Examinations Regulation.”
Despite anger among students, parents and teachers, Education Secretary Gavin Williamson insisted he would not follow the Scottish administration in doing a U-turn and allowing far more students to get results based on assessments from their school.
“You’ve got to have a system that has checks and balances, that looks at the whole performance and making sure you maintain standards within the exam system, to ensure those results carry credibility,” Mr Williamson told Sky News.
Prime Minister Boris Johnson also acknowledged the situation was going to be “very difficult” in the absence of formal examinations, but insisted the exam results published in England are “robust” and “dependable”.
But the Government is now under increasing pressure to review its moderation and appeals system.
Ministers were accused on Friday of lacking the courage to request a parliamentary recall so they can face MPs over the controversy.
The SNP’s Pete Wishart asked Speaker Sir Lindsay Hoyle to assure the Government he would look “sympathetically” on any request from them to interrupt the House of Commons summer recess to debate the grading system in England.
Mr Wishart added that the Speaker’s Office replied to his letter by stating Sir Lindsay would be “supportive of a recall in the current circumstances”.
But only the Government can make such a request and Mr Wishart conceded this is unlikely to happen.
The House of Commons is due to return from summer recess on September 1.
Mr Wishart, the MP for Perth and North Perthshire, said: “I think there’s absolutely no chance whatsoever that the Government is going to expose itself to this type of scrutiny.
“I’ve seen some of the representations from young people from all across England furious with what’s happened and I’m pretty certain they’d like to see a ministerial statement.
“But I do not think this is a Government that would have the courage to face the House under this current set of conditions.”
He added: “I think it’s pathetic.
“What we saw with Scotland was a government that came to the House, issued a statement, which faced a vote of confidence, which took questions, had a proper debate about the whole issue and we have Westminster just running away from any type of scrutiny.”
Mr Wishart said the Government should follow the Scottish Government’s lead and rely on the assessment of teachers and not use “woeful” algorithms.
A House of Commons spokesman, when asked if the Speaker’s Office could release details of Sir Lindsay’s letter, declined to comment on discussions between the Speaker and individual MPs.