London: Islamic extremist influence on the five Birmingham schools, placed into special measures following concerns about a hard-line takeover, remains a concern, a UK watchdog has warned.
Ofsted said that significant problems still exist at the five schools that were inspected on an unannounced basis over five days in September.
Inspectors raised concerns it had taken too much time to appoint new governors and senior leaders at these schools.
In a letter to UK education secretary Nicky Morgan, Ofsted chief Sir Michael Wilshaw said "too much poor practice remained unchallenged during the summer term".
He called on the Department for Education to intervene more quickly in academies by replacing trustees and school governors, and to require Birmingham to share its plans with the schools regulator.
A spokesperson for the Department for Education said the Ofsted reports were "a snapshot".
"They reflect the particular circumstances of the schools and the time at which the inspections took place, in some cases just a couple of days into the start of the new school year," he said.
"We are confident that the strong leadership teams we have put in place mean that change will be rapid and effective once it has had more than a few weeks to have an impact," he added.
Investigations were conducted into the allegations sparked by a "Trojan Horse" letter earlier this year that referred to an alleged plot by hard-line Muslims to take control of a number of governing boards in Birmingham.
In June, Ofsted issued a highly critical verdict on the running of a number of the city's schools and declared five failing, placing them into special measures.