Just how many Yorkshire children are in unregistered, illegal '˜schools'?

His warning comes two months after Bradford Council was told it was “in denial” over the city’s illegal and unregistered schools.

Inspectors have identified 100 suspected unregistered schools across the country since a team was set up in January to investigate the problem.

Last month, inspectors issued seven warning notices to suspected illegal schools in London, Birmingham, Luton, Wolverhampton and Staffordshire, where they found around 350 children on the premises.

In a letter to Education Secretary Nicky Morgan, he said inspectors had been “deeply alarmed” by some of the issues they have found.

He told her: “The evidence that they have gathered so far during this short period firmly reinforces my belief that there are many more children hidden away from the view of the authorities in unregistered schools across the country than previously thought.”

Sir Michael added: “What we have found so far is likely to represent only a small proportion of the illegal schools operating across the country. Inspectors are hearing about suspected new cases every week.

“I therefore remain extremely concerned about the number of children and young people attending these schools who may be at significant risk of harm and indoctrination.”

Ms Morgan asked Sir Michael last year to set up a new Ofsted taskforce to investigate suspected illegal schools, and pursue those responsible for running them.

Inspections uncovered “serious fire hazards, including obstructed exits and inaccessible fire escapes”, as well as schools with unsafe and unhygienic premises.

One case involved the discovery of “chemicals and chemistry equipment in an unlocked food cupboard in a room where children ate their lunch”, Sir Michael said.

Staff and volunteers were also found to have not been properly checked or cleared to work with children.

There is also a “clear link” between the growth of unregistered schools and the steep rise in children being home-educated in England in the past few years.

Sir Michael said those operating unregistered schools are “unscrupulously” using the freedoms parents have to educate their children at home as a cover for their activities.

He wrote: “They are exploiting weaknesses in the current legislation to operate on the cusp of the law. Many are charging parents thousands of pounds to send their children to these unregistered schools.

“In doing so, many are providing a sub-standard education, placing children at risk and undermining the Government’s efforts to ensure that all schools are promoting British values, including tolerance and respect for others.”

He called on local authorities to show vigilance and share intelligence with agencies including Ofsted so unregistered schools can be quickly identified and investigated, and said he has asked inspectors to write to councils after an inspection of an unsafe or unsuitable setting.

In November, Sir Michael asked Ms Morgan for Government support to ensure Ofsted has the resources to identify and support the prosecution of illegally operating schools, and in his letter said he was “grateful” for the what she had made available.

He also said he welcomed the new legislation the Government intends on unregistered and supplementary schools, adding: “I know we both share a determination to take swift and decisive action against those who are operating illegal schools and thereby putting children at risk of harm, including the risk of exposure to extremism and radicalisation.”

In March, Sir Michael criticised Bradford Council for not getting a grip on illegal schools that could be operating in the city as he hauled authority staff into a crisis meeting.

MP Naz Shah said the council was in “denial” over the city’s school system.

An Ofsted spokeswoman declined to say if any of the 100 suspected unregistered schools mentioned in Sir Michael’s letter were in Yorkshire.

Earlier this year the Yorkshire Post reported that it was believed that around 500 children were home schooled across Bradford, split 50/50 between the white and Asian population. But Sir Michael’s latest warning suggests the figure could be much higher.