Pupils at independent schools are significantly more likely to receive extra time to complete their exams, according to analysis of GCSE and A-level entries last year.

The research suggests that one in five students in independent schools received extra time to complete GCSE and A-level exams last year, compared with one in eight among their state counterparts. Pupils receive additional time because of a range of special educational needs or learning disabilities such as dyslexia.

According to analysis by BBC Radio 4’s Today programme, extra time was given to more than 27,000 independent school students in last year’s GCSE and A-level exams – nearly 20% of all pupils in the sector.

In contrast, in the state sector, less than 12% of students (200,000) received extra time.

Speaking on the Today programme on Friday, Peter Hamilton, headteacher at the Haberdashers’ Aske’s boys’ school, said the figures represented a “good news story”.

“For a long period of time, people have been getting better and better at identifying pupils’ special needs,” he said. “It’s a wonderful thing we’re now noticing some of these problems and beginning to get pupils to get fairness when they sit their examinations.”

Asked whether the gap between independent and state students receiving extra time was “suspicious”, Hamilton replied: “No, on the contrary, it’s not. It’s all to do with better tracking, better diagnosis, responding to pupil need.”

But Lucy Powell, a former Labour shadow education secretary, described the difference as “alarming”.

“I don’t know what the levels should be and what I think is worrying, in fact probably alarming, is the discrepancy between the independent sector and the state school sector,” said the Labour MP on Today.

Powell said Ofqual, the examinations regulator, should be looking at why the gap exists.

“It’s their job to look at and to make sure there is not an unfair advantage for whatever reason for those children,” she said.

“Across the independent sector there are fewer children with special educational needs, around 14%, and in the state sector it’s around 16%, so the independent sector are outperforming doubly themselves in getting this extra support in exams.

“It’s Ofqual’s job – and if it’s not their job then the [Department for Education] should make it their job – to make sure there’s a level playing field here.”

HMC, a group representing independent schools, told the BBC the higher rate was down to “proper resourcing” which it said could “be lacking in state maintained schools”.