Girls can marry at the age of nine, should ideally have husbands by 16 or 17 and should not be corrupted by going to work, according to a treatise published by female Islamic State supporters in Iraq and Syria.

The document, Women of the Islamic State: Manifesto and Case Study, says women must stay behind closed doors and leave the house only in exceptional circumstances.

“It is always preferable for a woman to remain hidden and veiled, to maintain society from behind this veil,” the English translation says. Fashion shops and beauty salons are denounced as the work of the devil.

The semi-official Islamic State manifesto on women – believed to be the first of its kind – was published on a jihadi forum in Arabic last month and is purported to be by the media wing of the al-Khanssaa Brigade, an all-female militia set up by Islamic State (Isis).

It has now been translated into English by the London-based counter-extremism thinktank Quilliam Foundation.

The introduction to the treatise says it has not been sanctioned by “the state” – meaning Islamic State – or its leadership but is a document to “clarify the role of Muslim women and the life which is desired for them” and “to clarify the realities of life and the hallowed existence of women in the Islamic State”.

The manifesto says: “From ages seven to nine, there will be three lessons: fiqh (understanding) and religion, Qur’anic Arabic (written and read) and science (accounting and natural sciences).

“From 10 to 12, there will be more religious studies, especially fiqh, focusing more on fiqh related to women and the rulings on marriage and divorce. This is in addition to the other two subjects. Skills like textiles and knitting, basic cooking will also be taught.

“From 13 to 15, there will be more of a focus on sharia, as well as more manual skills (especially those related to raising children) and less of the science, the basics of which will already have been taught. In addition, they will be taught about Islamic history, the life of the prophet and his followers.

“It is considered legitimate for a girl to be married at the age of nine. Most pure girls will be married by 16 or 17, while they are still young and active. Young men will not be more than 20 years old in those glorious generations.”

The western model for woman has failed, the treatise says, with women who go to work taking on “corrupted ideas and shoddy-minded beliefs instead of religion”. “The model preferred by infidels in the west failed the minute that women were ‘liberated’ from their cell in the house,” it says.

The manifesto includes a lengthy condemnation of the culture of the “disbelievers of Europe”, urging its readers to disavow “falsity and materialism in civilisation” and to devote oneself instead to religious knowledge.

The ideal Islamic community, it says, should not be caught up with “trying to uncover the secrets of nature and reaching the peaks of architectural sophistication”. They should instead concentrate on the implementation of sharia law and the spreading of Islam.

In a section entitled: “How the soldiers of Iblis [the devil] keep women from paradise”, the authors take aim at the western lifestyle that encourages both men and women to gain an education and employment. The manifesto denounces the wearing of fashionable clothes and piercings, concluding: “This urbanisation, modernity and fashion is presented by Iiblis [the devil] in fashion shops and beauty salons.”

It is the “fundamental function” of a woman to be in the house with her husband and children, the jihadi guide says, adding that they may leave the house to serve the community only in exceptional circumstances – to wage jihad when there are no men available, to study religion, and female doctors and teachers are permitted to leave but “must keep strictly to sharia guidelines”.

“Yes, we say: ‘Stay in your houses’, but this does not mean, in any way, that we support illiteracy, backwardness or ignorance,” the English-language translation reads. “Rather, we just support the distinction between working – that which involves a woman leaving the house – and studying, as it was ordained she should do.”