A student, rejected by her chosen university after her A-level results were downgraded, has told schools minister Nick Gibb he "ruined my life".
Speaking on BBC's Any Questions, Nina, from Peterborough, said her marks were three grades lower than predicted.
She told Mr Gibb she was distraught after failing to meet her offer from the Royal Veterinary College.
The government says it will cover the cost of appeals after 280,000 students in England had their marks downgraded.
Ministers are also expected to set up a taskforce, led by Mr Gibb, to oversee the appeals process.
After this summer's exams were cancelled due to the coronavirus pandemic, grades were awarded using a controversial modelling system, with the key factors being the ranking order of pupils and the previous exam results of schools and colleges.
In England, 36% of entries had grades lower than their teachers predicted and 3% were down two grades, prompting anger among schools, colleges and students.
Confronted by Nina Bunting Mitcham on Friday's Any Questions, Mr Gibb promised the appeals process would be "robust".
Nina, a pupil at New College, Stamford, was predicted to achieve ABB and scored As and Bs in her mock exams but was handed three D grades.
"It's got to be a mistake, I have never been a D-grade student.
"I feel my life has been completely ruined, I can't get into any universities with such grades or progress further in my life," she told Mr Gibb.
Mr Gibb said it was "rare" for students to be downgraded three grades from their predicted grades.
"This should not have happened to you. We don't want you to have to go through this," he responded. "It won't ruin your life, it will be sorted, I can assure you."
He added: "There will be these mistakes… we do know there are imperfections somewhere in the system as a result of this model. There are no models that can improve on that, this is the problem."
Image copyright PA Media Image caption There has been widespread concern about the fairness of the 'calculated' resultsSamantha Smith, a grammar school student from Telford, told BBC Radio 4's Today programme that her results had been downgraded from As and A* grades to a B, E and U.
"I know I didn't sit the exam but I didn't think I'd be treated as if I didn't turn up for the exam," she said.
"I've now got no university places, because of the algorithm and the system of being treated as if your postcode matters more than your potential."
Mr Gibb has said challenged grades will be addressed "swiftly", by September 7 at the latest.
He also advised that many universities had stated they would hold places open to start in January, giving students the option to sit exams this autumn.
Oxford's Worcester College said it would honour all offers it made to UK students, irrespective of their A-level results.
Admissions tutor Prof Laura Ashe said it was "the morally right thing to do".
Because students had not taken any exams, "we took the view there wasn't going to be any new information that could justify rejecting someone to whom we'd made an offer", she said.
She said the algorithm used to adjust grades "literally copied the inequalities that are currently existing in our education system", with a quarter of the college's state school applicants being downgraded, but only 10% of private school candidates.
Ofqual adjusted the results to make the spread of grades look right at a national level, she said, but "they can't possibly tell us that they've given the right grades to the right people".
Meanwhile, Greater Manchester Mayor Andy Burnham said he was investigating legal grounds to challenge the grading system, because it was "straightforwardly discriminatory" against working class and ethnic minority students who are more likely to attend large, urban sixth form colleges.
"I cannot stand by and see thousands of lives ruined across Greater Manchester," he told BBC Breakfast.
'Cold comfort'
Earlier, Labour called on ministers to act immediately to sort out the "exams fiasco" in England and to stop thousands of A-level students being "betrayed".
The Liberal Democrats welcomed the announcement over appeals costs, but called on Mr Williamson to resign.
The party's education spokeswoman, Layla Moran, said: "For the young people who have worked so hard to not get the results they deserve, through no fault of their own, this announcement alone will be cold comfort."
She added: "Ultimately, after Gavin Williamson's botched handling of the process thus far, pupils will have no confidence in him to fix the broken glass. Before he causes any more hurt, he must go."
Since the results came out on Thursday, there have been calls to move away from the chosen system and to use teachers' predictions, in the way that the government U-turned in Scotland. Labour said the government was squarely to blame for sticking with a "fatally flawed results system".
But England's exam watchdog Ofqual has warned that using teachers' predictions would have artificially inflated results - and would have seen about 38% of entries getting A*s and As.
Prime Minister Boris Johnson has previously defended what he said were a "robust set" of grades and said that pupils who believed they were treated unfairly would be able to appeal or, if they wanted, sit exams in the autumn.
Schools can appeal for an upgrade if their pupils' mock grades were higher than their estimated results. Education Secretary Gavin Williamson told The Times the government would cover the fees in a bid to ensure that head teachers were not deterred from making appeals.
There had been fears that appeal costs - which can reach £150 - could stop schools from taking on harder to prove cases.
But the exam regulator Ofqual has still to say how a mock exam result can be validated - and head teachers have warned that mocks are not standardised or taken by all pupils, and could not be used as a fair way of deciding final exam results.
Ofqual has promised more details next week.