The troubled King Science Academy in Bradford is not doing enough to raise standards, the schools watchdog has said.

In a letter published by Ofsted, it says that more needs to be done to tackle areas of greatest concern, particularly around leadership, improving the curriculum and hiring experienced teachers.

The observations followed the second visit made by Ofsted inspectors since they first judged the free school as requiring improvement this time last year.

The school was then hit by scandal after the Department for Education investigation into the school made allegations of fraud.

West Yorkshire Police is now investigating claims that the school fabricated invoices in order to claim taxpayers’ cash. The criminal investigation led to the arrest of the school’s founder and principal Sajid Raza. He was later released on bail.

The incident was of particular embarrassment to prime minister David Cameron, who gave the school his personal endorsement when he visited the flagship free school on Budget day back in March 2012. 

And now, in yet more problems for the school, inspectors have urged the school to take “immediate action” to secure additional, experienced leadership and teaching staff.

Senior leaders and governors were “not taking effective action to tackle the areas requiring improvement” identified at the last inspection, the watchdog says in its letter.

It refers to Mr Raza as being “absent long term” and points out that in September last year 29 new teachers joined the school to cater for a new year group, 19 of which were either newly qualified or trainees.

As a result, inspectors said teaching was “persistently inadequate”, despite procedures being put in place to monitor the quality of teaching.

The letter, from HMI Jane Austin, adds: “A coherent plan for the Key Stage 4 curriculum is not in place and so decisions about recruiting staff for the coming academic year are tardy.”

Ms Austin did recognise, however, that some “significant decisions had been implemented” and that “governance was improving”.

Senior leaders, she adds, working very closely with the chair of the governing body, had accelerated the academy’s development.

TES contacted the free school for comment, but was told that no staff were available.

The National Union of Teachers (NUT) said it never welcomed news that a school was failing to provide a high standards of education, but added that it was “disturbing” to note that not enough action was being taken by the school’s leadership team.

“If this were a maintained school, then the governing body would by now have been removed and an interim executive board put in its place, an action that the local authority would have been able to take to put the school back on track,” NUT general secretary Christine Blower, said.

“As [King Science Academy is] a free school, the secretary of state has ultimate responsibility for ensuring that corrective action is taken and it is surprising to say the least that firmer action has not been taken against this school.”