Private school watchdog the School Inspection Service has closed down after Ofsted found concerns with its rigour and approach to safeguarding.

In a letter to the education secretary, chief inspector Amanda Spielman called for the government to close down underperforming Steiner schools that fail to improve.

She also highlighted failings in the School Inspection Service (SIS), which had been responsible for monitoring the largely privately run Steiner schools and some religious schools.

“The results of our monitoring work of SIS also gave me cause for concern: the inspections we monitored lacked rigour, particularly in relation to safeguarding,” Ms Spielman wrote to Damian Hinds.

“I am aware that SIS has taken the decision to cease operating. I know our officials are already working together, along with the Independent Schools Inspectorate (ISI), to ensure that all schools previously under the SIS umbrella are inspected by an alternative inspectorate.”

In November Mr Hinds commissioned Ofsted to inspect some Steiner independent schools and step up its monitoring of the quality of SIS inspections.

Ms Spielman had complained that Ofsted’s oversight of the quality of SIS and ISI inspections had been “seriously hampered” by the small number of reviews commissioned by the DfE.

The SIS board of directors in a statement said they had “resolved in September, 2018 that the Company would cease to inspect schools in England and Wales and the Department for Education were notified of this decision”.

“After further consideration of timescales it was decided that this decision would be implemented with effect from the 1st January, 2019 and the appropriate bodies were notified.

“The Board of the School Inspection Service is proud of its record of inspection over a number of years and wishes all schools with which it was associated well for the future.”

A spokesperson for Ofsted referred questions about the SIS closure to the Department for Education.

A spokesperson for the DfE confirmed that the SIS’s “closure is not linked to the Steiner standards,” but refused to give more details.

A separate organisation, the ISI, monitors more than 1,000 larger independent schools. It has been feeling the pinch in recent years.

The last available accounts for the body, from 2017, revealed it had been operating at a loss for two years while its reserves had plunged from £2.3 million in 2013 to £236,000.

The ISI hiked fees for its members by 12 per cent in 2018 in a bid to “build up reserves to cover the higher cost years” and instituted a cost reduction programme.