Sir Michael Wilshaw has warned that leaders in some independent Islamic schools are continuing to undermine British values, after inspectors found more evidence of gender segregation.

In a letter to Nicky Morgan, Secretary of State for Education and Equalities Minister, the Ofsted chief wrote that inspectors "continue to find that staff are being segregated because of their gender in Muslim independent schools."

Ofsted Inspectors who inspected the Rabia Girls' and Boys' School in Luton "expressed their concern when, at the initial meeting with inspectors, the school insisted on segregating men and women through the use of a dividing screen across the middle of the room," he wrote.

In addition to the gender segregation in that meeting, inspectors "gathered evidence that male and female staff are segregated during whole-school staff training sessions. Male staff sit in one room and the session is simultaneously broadcast to female staff in another part of the school," Sir Michael wrote.

Despite improvements in the "inadequate" school elsewhere since the last inspection, the Ofsted inspectors "were so concerned about the behaviours modelled by the leaders of this school they informed the proprietor that the school would remain in the inadequate category despite improvements being made elsewhere."

Between 12 April and 21 April 2016 three inadequate faith schools were subject to emergency follow-up inspections by Ofsted, at the request of the Department for Education, and inspectors found extensive evidence of gender segregation.

Sir Michael said the pattern of gender segregation "clearly does not conform to the spirit of the equalities legislation".

The Chief Inspector added that despite the 2014 instructions issued by the DfE that all schools have a duty to "actively promote" British values, it was "clear" that these rules "are not being followed by some independent schools."

He went further and said that British values in some Islamic independent schools "are being actively undermined by some leaders, governors and proprietors."

Ofsted would remain tough in dealing with gender segregation he said, and any form of "segregation, without a good educational reason, is likely to lead to an inadequate inspection judgement for leadership and management."

Sir Michael has urged the Secretary of State "to further review the DfE guidance to independent schools on these matters and, if necessary, write to the proprietors of independent faith schools to clarify your expectations and to reaffirm the government's commitment to the promotion of British values."

In November 2015 Ofsted raised serious concerns about gender segregation in Islamic schools. In 2014 it warned that there was a "serious risk" to students' physical and/or educational welfare in six Islamic schools.

NSS campaigns director Stephen Evans said it was "very welcome to see Ofsted holding failing independent faith schools to account".

"We owe it to children and young people to ensure that all schools are held to certain standards regardless of how they're funded. Any school which enforces segregation against their own staff, discriminates against women and fails to give children the education they deserve isn't worthy of being called a school."