School inspector Ofsted and the Department for Education let down Birmingham pupils, a damning Commons inquiry into the Trojan Horse affair has warned.

MPs said exam results had fallen in schools at the centre of claims some governors and teachers had attempted to impose an Islamic identity on them.

The Commons Education Committee warned there was “crisis and confusion” caused partly by the failure of Ofsted, the Government and Birmingham City Council to work together.

MPs said it was impossible to have confidence in Ofsted, which gave some of the schools glowing reports before the scandal broke.

The committee looked at how official bodies responded to a letter sent to Birmingham City Council in November 2013, which became public in March 2014 and appeared to reveal details of a plot called “Trojan Horse” to take over city schools.

While the letter now appears to have been a fabrication, an inquiry by Ian Kershaw, the independent adviser appointed by the council, found some governors, teachers and parents “had been seeking to promote and encourage Islamic principles in the schools” and “objected to parts of the school curriculum that are viewed as anti-Islamic – sex education, or citizenship.”

In a new report, MPs warned there had been too many inquiries into Birmingham schools – with Ofsted, the Department for Education, the Education Funding Agency, the council and police all conducting investigations. They said: “The number of overlapping inquiries contributed to the sense of crisis and confusion, and the number of reports, coming out at different times and often leaked in advance, was far from helpful.”

The Department for Education was “slow to take an active interest” after it received the Trojan Horse letter in December 2013, four months before the letter became public, MPs said.

They warned that exam results had fallen at the schools affected. Results at Park View dropped significantly in 2014 from 75 per cent of pupils gaining five or more GCSEs at grades A* to C in 2013 to just 58 per cent in 2014. They said: “The children in the schools affected in Birmingham deserve better from all involved.”

The public could not have confidence in Ofsted after it gave some of the affected schools glowing reports – only to decide they had serious problems after the Trojan Horse letter emerged, MPs said.

For example, Oldknow Academy in Small Heath was inspected in January 2013 and judged to be outstanding but was placed into special measures when it was inspected again in April 2014. The MPs said: “Confidence in Ofsted has been undermined and efforts should be made by the inspectorate to restore it in Birmingham and beyond.

“Whistleblowers had tried to raise concerns about Birmingham schools but had been ignored.

“One of the facts which emerged quickly from the Trojan Horse story was that the difficulties faced by the schools had been brought to the attention of Birmingham City Council and the Department for Education on several occasions prior to the receipt of the anonymous letter.”

Graham Stuart, chairman of the Education Committee, said: “We found a worrying and wasteful lack of co-ordination between the various inquiries carried out by the DfE, Birmingham City Council, the Education Funding Agency, Ofsted and others.” He added: “The British values which are now to be promoted in all schools are universal and deserving of support. Monitoring how these are promoted in individual schools must be done with common sense and sensitivity.”