Amanda Spielman, the chief inspector of schools watchdog Ofsted, made the claim on Wednesday against unregistered schools to the UK Parliament’s Public Accounts Committee.

Ms Spielman wrote a letter calling for new powers to tackle irregular unregistered schools, which operate without permission and teach a limited, extremist faith-based curriculum.

Amanda said: “My inspectors have been shocked by what they have found in these schools (…) in some schools we see the extremely worrying material.”

Spielman explained: “We have, for instance, found books that say it is acceptable for men to use physical violence against their wives, texts that say it is unacceptable for women to refuse sex to their husbands and literature calling for the death of gay people.

“These texts have no place in young people’s education.”

Spielman said: “This material has been found in poorly performing registered independent schools and even in a maintained community school, but also in unregistered schools, where our powers to tackle it are far more limited.”

She explained that Ofsted’s “current lack of powers to seize evidence means that we are tackling this problem with one hand tied behind our back.”

The school inspector’s letter adds that “the number of children disappearing from the formal system and into unregulated, unregistered provision (…) is perhaps my greatest concern as chief inspector.”

Elsewhere in the letter, the chief inspector warned about the undue influence of outside groups advocating “for changes in school policy on the basis of religion or culture” in schools across the UK, which “can lead to the curtailing of rights of other protected groups.”

The Ofsted report said: “The new standards on fundamental British values look at requirements in relation to written policies on the curriculum, the quality of teaching and the spiritual, moral, social and cultural development of pupils.

“While numbers are small, a higher proportion of the weaker faith schools are failing on these requirements when compared to those with no faith.”

According to Ofsted figures, 81 out of 139 independent Muslim schools were found to be less than good at their most recent inspection, while 39 were inadequate. One-third of Christian schools were judged less than good, and of 58 Jewish schools, more than half were either “requires improvement” or inadequate.

Independent special schools are, in contrast, making strong progress, with 78% judged good or outstanding, up from 74% in 2014, while only 9% were judged inadequate compared with 19% of other independent schools.