The proportion scoring worse than a good ranking rose from 31 per cent to 40 per cent in the last year, Ofsted will reveal in its annual report on Wednesday.
The regulator of UK classrooms said: "A number are highly conservative Christian, Jewish, or Muslim faith schools.
"In some of these schools, the premises are unsafe or squalid.
"The most basic checks are not always in place."
Inspectors will also report that some independent faith schools were found to be harbouring "sexist and sectarian literature".
They warned that an "increasing number" of "conservative" religious schools "are spreading beliefs that clash with British values and equalities laws".
Ofsted added: "To function effectively, British society depends on some fundamental shared values as well as a culture of mutual tolerance and respect."
In the annual report, the Chief Inspector of Schools is also expected to reveal that 90 per cent of all primary schools and nearly 80 per cent of all secondary schools are now rated either good or outstanding.