Top universities are giving privately educated children an unfair advantage by not differentiating between the rigorous GCSEs compulsory in the state system and less demanding exams taken in many fee-paying schools, MPs and educationists have said.

Just days after GCSE results day last Thursday, Freedom of Information (FoI) requests by Labour MP Lucy Powell show that almost all Russell Group universities treat the two types of exam – the regulated GCSEs used in the state system, and IGCSEs, which the government admits do not meet the same high standards – as exact equivalents in admission processes.

This weekend, Robert Halfon, the Conservative MP who chairs the Commons education select committee, said it was extraordinary that state school pupils were taking harder exams than their private school counterparts, and that these qualifications were then treated as the same by universities. “The priority has to be a level playing field,” Halfon said. “I find it extraordinary that … pupils in private schools, who start with many advantages, are then able to take inferior exams. Everyone should have the chance to climb the education ladder, without unfair advantage to those in private schools.”

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Responding to FoIs requests from Powell, only Cambridge University among the 24 Russell Group universities said it did not take exam results at key stage 4 (14-16 years) into account when deciding which students to admit. The other 23 said they did take them into account and made no distinction between the two.

Powell, a former shadow education secretary, called on the government to act to ensure state school pupils were no longer disadvantaged in the race for places at top universities. She said: “It’s an absolute scandal that it is easier to get top grades in IGCSEs than in the new GCSEs, yet universities essentially class them as the same. State schools do an excellent job – often in difficult circumstances, and now with reduced funding – to help young people get the best GCSE results they can. There’s been a lot of turmoil with the new system, which private schools, by shirking away from the new GCSEs, have shielded their pupils from.”

Facebook Twitter Pinterest Like many private schools, St James Senior Boys’ School, Surrey, offers pupils IGCSE exams in several subjects. Photograph: Greg Balfour Evans/Alamy

She called on ministers and Ofqual, the exam regulator, to conduct an urgent review of admissions criteria in order to restore fairness and direct universities to ensure the tough new GCSEs were properly counted.

Peter Hyman, founder of School 21, a state-funded school for children aged four-18 in east London, said: “Private schools already have a lot stacked in their favour. To have a two-tier system in which no account is taken of the fact that one system is harder is obviously wrong.”

Earlier this year the chair of Ofqual, Roger Taylor, told the education select committee that the current system “is not conducive to public trust in the examination system”. A spokesman for Ofqual said last night: “People should be careful when using GCSE and International GCSEs interchangeably … However, we recognise that such precise comparison might not be an issue for everyone. Universities and employers are used to seeing many different qualifications on applications and deciding what value they place on them.”

In 2017-18, before IGCSEs were dropped from the state system, 91% of IGCSEs in core (EBacc) subjects such as English, maths, and sciences were taken in independent schools. A pupil in an independent school was 136 times more likely to sit an IGCSE.

The Department for Education, which reformed the GCSE system when Michael Gove was education secretary, admits that the new exams are more rigorous than those still widely used in the private sector.

When the Observer first raised the issue last December the DfE said: “International GCSEs have not been through the same regulatory approval and quality control as the new gold-standard GCSEs, which is why we no longer recognise international GCSEs in school performance tables. The new GCSE qualifications have been reformed to provide more rigorous content, so young people are taught the knowledge and skills they need for future study and employment.”

A DfE spokesperson said this weekend: “Independent schools are by definition independent and make their own decisions about what qualifications to offer. If a school decides to offer international GCSEs instead of reformed 9-to-1 GCSEs, it will not get credit for them in performance tables. This is because we want to ensure pupils benefit from reformed 9-to-1 GCSEs, which are the gold standard qualification at 16, in line with expected standards in countries with high performing education systems.”