Pupils eligible for free school meals were less than half as likely to get top grades at GCSE than their more privileged peers, new analysis shows.
Exams regulator Ofqual said poorer pupils in England had fallen further behind wealthier students by around a tenth of a grade compared to 2019 under a "long-standing results gap".
Fewer than 14% of grades for students on free school meals were Level 7 (A) or above compared with over 31% for pupils who are not eligible for the benefit.
Ofqual pointed to the "uneven impact" of the Covid pandemic for the widening attainment gap for free school meal pupils.
Labour claimed the Government had "abandoned" children eligible for the benefit, after chaos over the policy during the pandemic and criticism of the slow rollout of laptops to help needy pupils learn at home.
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Private schools also outstripped state schools, with 62% of private school grades at Level 7 or above, compared to 26% for comprehensives.
This gap has increased by nearly a fifth over the last four years, according to analysis by Labour.
It comes as hundreds of thousands of young people opened their results on Thursday, with nearly three in 10 (28.9%) awarded the top grades, compared to 26.2% last year.
Marks were awarded by teachers after exams were cancelled for the second year in a row due to Covid chaos.
Analysis by Ofqual found no notable changes in the gap between the grades received by white pupils and those received by most ethnic groups.
But Gypsy and Roma pupils have seen a decrease in outcomes compared with 2019.
Grammar schools saw 68.4% of entries achieve a top grade this year, while 28.1% of pupils at academies were awarded a grade 7 or higher.
Geoff Barton, general secretary of the Association of School and College Leaders, said any increase in the divide between schools was "worrying".
"The most likely explanation is that pupils at independent schools have in general been less affected by the pandemic than those at state schools," he said.
"They are more likely to come from wealthy homes where digital technology will have been readily available and they are generally taught in smaller groups because independent schools are much better funded than state schools.
"This does emphasise the need for a much more substantial education recovery package for the state sector than ministers have so far provided."
Social mobility charity the Sutton Trust raised concerns on A-level results day that the pandemic had widened the gap between private and state schools.
Chairman Sir Peter Lampl said: "GCSEs are a pivotal moment in a young person's life: they're passports to next steps, whether that's further study or training.
"The attainment gap between disadvantaged pupils and their peers has also increased due to the effects of the pandemic, which have impacted disadvantaged students most keenly.
"As these students have faced the most obstacles in their learning this year, it's crucial that there is support for their learning as they enter post-16 education ."
Shadow Education Secretary Kate Green said: "Children on free school meals have been abandoned by this government and students in state schools are again being outstripped by their more advantaged private school peers.
"These widening attainment gaps are testament to the Conservatives' failed approach to education."
Skills minister Gillian Keegan said private schools had performed better in GCSE results because they are selective.
Asked about the results gap, she told BBC Radio 4's World At One programme: "Some fee-paying schools, it is something we see every year - that's why we are always focused on the disadvantaged gap.
"One of the things we did see this year is that actually all students did improve overall - that's great news, and there was stability in the results at all levels, so we're delighted for all the students.
"But you do see some differences in those private schools because they are selective schools."
