Using grades with asterisks in 2021 to flag students’ missed learning time owing to Covid risks “muddying the waters” for employers and higher education providers teachers’ leaders have warned.

The news comes as the shadow education secretary Kate Green accused Gavin Williamson of leaving school students in “horrible and uncertain limbo” by not announcing exam plans until December.

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This morning, Tes revealed that the government’s expert group on differential learning loss during the pandemic could suggest students badly affected by Covid-19 receive grades with an asterisk or code to show how the pandemic had impacted their learning.

But Mary Bousted, joint general secretary of the NEU teaching union, has said the use of these codes could risk undermining students’ grades.

“There are real problems with that asterisk because what that says is, this student has had such difficulties that this exam grade is likely not to reflect their potential or their ability, so what does that say about the exam grade?” she said.

“It muddies the waters - I don’t know how people will take that, I don’t know how employers or sixth-form colleges will take that because what it says is this exam probably doesn’t give a reflection of that student’s potential, but what it absolutely doesn’t do is say what their potential is.

“So as far as I’m concerned that’s not really a mitigating factor, I don’t see how that’s going to help those students whose grades are artificially lower because their education was so disrupted, because it doesn’t give you any idea about how much it’s been disrupted and what grade they would have got if they had had an uninterrupted education.”

And today, Ms Green told the House of Commons that the proposals from the Department for Education fell short of the fair exams that the education secretary had promised.

She claimed that had the department acted sooner, it could have done more to ensure next year’s exams would be fairer.

The government announced their full plans for exams today, which include ensuring grades are as generous as those awarded this year and that students have advance notice of some topic areas covered in GCSE, AS and A levels.

Responding to the announcement, Ms Green said: “The government has known since September that an ongoing pandemic would create huge challenges in schools and for months they’ll have heard school leaders, parents and members on this side of the House calling for a credible plan to address them. It’s taken until December to provide one.

“So can [Gavin Williamson] tell us what took him so long? Why did he leave students in a horrible and uncertain limbo? The truth is that the delay has limited the department’s options.

“Had they acted sooner, they could have done more to make the system fairer.”

She added: “I want students to have the chance to show what they’ve achieved in the most challenging of circumstances, but after months of silence these proposals fall short of the fair exams the secretary of state promised. This is at best a ‘requires improvement’”.

Mr Williamson responded: “I’m glad that (Ms Green) could bring herself to welcome the measures, slightly grudgingly, at the start and it’s no thanks to the party opposite that, actually, schools are back and children are in schools.”

He added: “The party opposite have never championed pupils because they haven’t fought to get students back into schools. It was actually the mayor of Greater Manchester (Andy Burnham) that wanted to send children out of school and back home.

“But this party stands for getting back into school.”

Ms Green welcomed measures to help pupils be assessed on what they’ve learned, that reserve papers will be in place for pupils who might miss out, that performance tables will be suspended and that routine Ofsted inspections will not resume in January.

However, she said today’s announcement still “bakes in fundamental inequities between students who’ve suffered different levels of disruption to their learning” through the impact of Covid-19.