Ofsted is in “a lot of trouble” and its chief inspector Amanda Spielman is “not a safe pair of hands,” a teaching union leader has claimed.

The criticism from Mary Bousted, joint general secretary of the National Education Union (NEU) has been sparked by Ms Spielman’s warning that disadvantaged teenagers are not being challenged enough with the reading materials they were given.

Dr Bousted, a former English teacher, said the chief inspector of schools had showed “a complete lack of understanding of the challenging nature of work in disadvantaged schools”.

She said: “Teachers in these schools have been trying to get children to understand that reading can be enjoyable, and to give them books which are appropriate to their reading age, and which allow them to get enjoyment by reading fluently, and not constantly having to decipher words they don’t understand or having to work their way through complex sentence structures.”

Her comments are only the latest in a long line of criticism for the increasingly embattled schools watchdog. 

Last week Dr Bousted attacked Ms Spielman on Twitter after the Ofsted boss commented in an interview on Radio 4 that there was no evidence  that funding cuts were harming education.

Also last week, the NAHT union of headteachers’ Accountability Commission concluded Ofsted could not deliver reliable judgements because of the lack of time and resources it has available to inspect schools.

That followed a criticism from the Public Accounts Committee when MPs called on Ms Spielman to speak out more, with chair Meg Hillier MP warning that Ofsted’s credibility could “evaporate” if school inspection is eroded any further.

This week Dr Bousted told Tes: “Ofsted is in a lot of trouble and I don’t think Amanda Spielman is a safe pair of hands.

“She has never taught and has a complete lack of understanding of the desperately hard work and the challenging nature of working in disadvantaged schools. On the one hand you get her saying she admires the work of teachers and on the other hand you get this constant criticism.”

An Ofsted spokesperson said: “The chief inspector has made clear her total respect and admiration for the life changing work of teachers in disadvantaged areas and the need to make sure that schools in these areas receive the support they need to improve.

“But she will also always be robust in challenging the notion that we should have lower expectations for young people from less affluent backgrounds. 

“Once again it is Dr Bousted providing the constant stream of criticism and negativity about the education system, rather than recognising the achievements of her own members.”