The government will “struggle to embed” reforms aimed at improving attainment if school oversight continues to be “confused and inconsistent”, Sir Michael Wilshaw will warn today.

The Ofsted chief inspector will use a speech to the CentreForum think tank this evening to call for “strong leadership” in education across England and for clarity over the roles of regional schools commissioners (RSCs).

His comments will follow a warning in a report released today by CentreForum and Education Datalab that the introduction of a new GCSE grading system could see the proportion of pupils achieving a “good pass” in the exams fall by almost a quarter.

Speaking in London today, Sir Michael is expected to say that the roles of RSCs and how they fit with other accountability bodies are “not always clear”, and will warn that there is currently a “patchwork of accountability”, rather than the “seamless cover” needed.

He will say: “At the moment, we have a confusing and ill-defined system of oversight and intervention. Problems, inevitably, are shuffled between various agencies. This isn’t fair on parents and it certainly isn’t fair on schools.

“A symptom of that confusion has been a more than doubling of complaints to Ofsted about schools in the last three years. The danger is that only those able to navigate this accountability maze will have their concerns addressed.”

Sir Michael will repeat fears raised in his annual report last year about the progress of children in secondary schools, particularly in parts of the north and midlands, and will warn about the impact of stricter pass levels on struggling schools in those regions, despite his own insistence that pupils and schools should “aim high”.

He will say: “CentreForum has set ambitious targets for English schools to meet at key stage 4. It is going to be a challenge for the average performing school’s students to reach the new minimum acceptable grade 5, assessed between the present C and B grade.

“How much harder will it be for children in struggling schools, disproportionately concentrated in the north and the midlands, to reach them from such a low base?”

A Department for Education spokesperson said: “We have already intervened in more than 1,000 schools over the past four years; pairing them up with excellent sponsors to give pupils the best chances.

“That compares with the years and even decades of neglect many schools suffered under local authority control. Academies operate under a strict system of oversight and accountability – more robust than in council-run schools — which means any issues are identified and swift action can be taken.”