Ofsted should consider how many pupils have private tuition when they inspect schools, its former director of corporate strategy has said.

Luke Tryl, who left the inspectorate last month to lead the free-school organisation the New Schools Network, said he had “unsuccessfully pushed” for the change when he was at Ofsted.

Last year, research found that a quarter of secondary school pupils supplemented their school lessons with private tutors. 

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In an interview with the Times, Mr Tryl said: “One of the things I unsuccessfully pushed for when I was at Ofsted was to take a keener look at the number of pupils using tutors. It gives you an indicator as to whether there is topping up from outside.

“People always focus on the dominance of private schools widening social inequality, but what is more pernicious is the growing use of tutors.

"It essentially means if you’re middle class you can top up your education – get a massive leg-up – if you’re working class you can’t.

"That to me is the epitome of a rigged system.”

He added that this meant schools in “leafy areas” see their results boosted by the extra tuition outside of school, “whereas schools in deprived areas are doing the job entirely themselves”.

Last year, an Ipsos MORI poll for the Sutton Trust found 27 per cent of 11 to 16-year-olds in England said they had used private tutors.

The figure was even higher in London, standing at 41 per cent.

At the time, Sir Peter Lampl, chairman of the Sutton Trust, raised concerns about the impact of this on educational inequality.

He said: "The fact that [private tuition] is predominantly used to help children do well in a specific test or exam means that those who can afford it are able to give their children a significant advantage over those that cannot.

"If we are serious about social mobility, we need to make sure that the academic playing field is levelled outside of the school gate by the state providing funding for private tuition on a means-tested basis."

The Sutton Trust called for the government to introduce a voucher system - funded by the pupil premium - to ensure that lower-income families could purchase extra educational support.

Asked to respond to Mr Tryl's comments, an Ofsted spokesperson said: "This isn’t something we’re looking at right now. The data about private tutors isn’t collected by schools, so we don’t know what impact private tutoring has."