An illegal faith school for ultra-Orthodox Jewish boys ran a hiking expedition to Dover in which a group of 34 children and two adults nearly drowned and had to be rescued by emergency services.

The students were dressed in ultra-Orthodox clothes instead of hiking gear during the outing on 6 June, and could not understand warning signs because they cannot speak English, according to The Independent.

Compounding the danger, organisers of the trip apparently first attempted to contact community leaders as the tide came in, instead of the emergency services amid fears over the school being discovered.

The school, which is based in Hackney, East London, bans 'secular knowledge' and only teaches religious texts in Yiddish and Hebrew. It is one of dozens operating illegally in the Stamford Hill area of Hackney, with up to 1,000 pupils attending lessons from 6am to 11pm in cramped buildings, an investigation by The Independent has revealed.

According to the investigation, the Government has known about the school which organised the hiking trip for five years, and a number of similar illegal schools for several years.

Pupils reportedly tried to deny they attended the school, claiming to be on a day out as a group of friends. But a reporter from The Independent visited the school site, where members of the public confirmed that the school was involved in the incident.

Internal documents seen by The Independent show that Hackney Council first knew about the school in 2011.

A spokesperson for GesherEU, a charity which supports people leaving the ultra-Orthodox Jewish community, said: "This is not the first time children's lives have been put in danger by, apparently, incompetent staff. Next time we could be seeing mothers wailing at the funerals of their sons or daughters unless ministers, the Department for Education and Hackney listen to our call for these settings to be properly monitored, for them to employ properly trained staff, and to ensure that these children are given the skills and secular education they will require to have choices and contribute to society when they are older.

"Both the Department for Education and Hackney continually say that they are liaising with each other, and nothing seems to happen. We know that the legislation relating to the monitoring, safeguarding and education standards in independent schools, unregistered settings and for home-educated children, is confusing and that it is inadequate when fundamentalist religious bodies are set on following their own narrow curriculum. We urge them to go to the ministers responsible to push through urgent changes to the legislation to give them the powers to make real change."