The proportion of entries gaining at least a C grade or 7 under the new English system – falls to 66.3%, the lowest since 2008.

Overall GCSE pass rates have fallen this year after a new grading system was introduced in England in the biggest overhaul in a generation.

Traditional A* to G grades have now been replaced with a 9 to 1 system, with 9 being the highest mark.

The grade 7 is broadly equivalent to an A under the old system, while a 4 is broadly equivalent to a C.

Three core subjects – maths, English language and English literature – are the first to be tested using the new numerical grading.

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Across England, Wales and Northern Ireland, the proportion of C/4 grades or above awarded to 16-year-old pupils is down 0.6% to 66.3% – the lowest since 2008

And the percentage of A/7 grades or above fell 0.5% to 20%.

The proportion of entries receiving G/1 or above was unchanged at 98.4%.

In England, around 18,600 maths entries (3.5%) scored a 9, while about 13,700 (2.6%) achieved the top mark in English language and more than 17,000 in English literature (3.3%).

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Last year, 4% of 16-year-olds in England scored an A* in English language, along with 7% in maths.

The grading switch is part of wider reforms designed to make GCSEs more rigorous and challenging.

This year, girls outperformed boys in 9 grades in both English GCSEs, while boys did better in maths at the highest result.

The course content for these subjects has been changed with the emphasis shifting from coursework to exams.

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In maths, there is also more content on topics such as number, ratio and proportion, and pupils have to show clear mathematical arguments for their calculations and remember key formulae.

In English language, pupils now have to read a wider range of texts from different genres and time periods, and more importance is given to spelling, punctuation and grammar.

In English literature, students have to read a wide range of classic literature, including 19th century novels, Shakespeare and the Romantic poets.

Schools minister Nick Gibb said: “The Government’s new gold-standard GCSEs in English and maths have been benchmarked against the best in the world, raising academic standards for pupils.

“These reforms represent another step in our drive to raise standards, so that pupils have the knowledge and skills they need to compete in a global workplace.”

Labour’s shadow education secretary Angela Rayner said: “Unfortunately the Government’s unnecessary tinkering with grades have meant that there are many parents and employers who are still struggling to understand what the results in maths and English actually mean.”

There are concerns that children sitting the new exams did not have enough time to prepare – less than two years instead of three – but the exam regulator Ofqual said these fears had been addressed.

Chief regulator Sally Collier said: “Today’s results reflect years of careful planning.