Prime minister Boris Johnson has been warned that he risks “robbing a generation of young people of their future” unless unfairness in the exams system is addressed.

Concerns have been raised by Labour that A-level and GCSE results could be downgraded for thousands of students in England because of the replacement grading system introduced due to coronavirus exam cancellations.

Last month, exam regulator Ofqual confirmed that standardisation would draw on the historical outcomes of a school or college.

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On Monday, Scotland’s first minister, Nicola Sturgeon, apologised to students in the country who felt they had unfairly had their results downgraded, and the country’s education secretary, John Swinney, said today that the downgrades would be reversed.

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Labour has now urged the UK government to carry out several changes to make the exams system fairer.

The party’s proposals include helping students to correct their grades, with credible appeals and resits, as well as urgently clarifying which students are likely to be worst affected by the model being used.

It also says the government should mandate greater flexibility in admissions decisions this year and ensure that no GCSE student will be moderated down to below a grade 4 in English or maths.

Labour Party leader Sir Keir Starmer said it was a “blatant injustice” that young people were having their futures decided by their postcode.

“Pupils and parents are rightly worried that years of hard work are about to be undone because a computer has decided to mark their child down,” he said.

“For too long the Tories have considered the needs of young people as an afterthought when their needs should have been central.

“It’s a blatant injustice that thousands of hard-working young people risk having their futures decided on the basis of their postcode.

“Unless Boris Johnson acts, he risks robbing a generation of young people of their future.”

Green Party education spokesperson Vix Lowthion said teachers should have been trusted in the grading process.

She said: “It has been an extremely difficult summer for schools, pupils and examiners, but basing grades on schools’ past attainments will punish disadvantaged students and only widen inequalities in our society.

“This has not been a normal year and there is no point in pretending it has been.

“Instead, teachers should have been listened to and trusted.

“Teachers are the ones who know their pupils best and are most qualified to say how they would have achieved.”

Ms Lowthion added: “The current system looks arbitrary and unclear.

“This is not the time to be gambling with people’s futures when so much is at stake, both for our young people and the country at large.”

Liberal Democrat education spokeswoman Layla Moran said: “Every individual should get the best start in life, whoever they are, whatever their background.

“These predicted grades will have a lasting consequence on a young person’s choices - that is why it’s crucial [education secretary Gavin Williamson] steps in to ensure that no one is disadvantaged by the pandemic or by their gender, ethnicity or socioeconomic status.”