Independent schools are only offering “crumbs off their tables” to state schools, and should make a far bigger effort to help them improve, the chief inspector of schools has said.

In a damning speech, Sir Michael Wilshaw told the country’s leading private school heads that many of the partnerships currently operating between private and state schools amounted to “thin stuff”.

Commonly used excuses for not helping the state sector could be overcome, he insisted in his address to the annual conference of the Headmasters’ and Headmistresses’ Conference of elite independent school heads.

He said it was “commendable” that a small number of schools were sponsoring or co-sponsoring academies and lending staff, but added: “For the vast majority of independent schools, the commitment and resource is far less - a bit of coaching for A-level students; the occasional loan of a playing field.

“I’m sorry to say, but the [Independent Schools Councils’] list of activities is hardly evidence of a comprehensive commitment to partnership with state schools. It’s thin stuff. These are crumbs off your tables, leading more to famine than feast.”

Continuing his tirade, he added: “It is hard not to conclude that too many in the independent sector are far more concerned with issues within their own walls than beyond them.”

In a call-to arms, he said private schools needed to “search their consciences” and “persist” against the perceived barriers to making partnerships work.

He added: “Parents and governors can be unsympathetic. A few of your colleagues exhibit antediluvian views. Some of them recoil from involvement in environments that can seem alien and daunting.

“None of these obstacles are insurmountable. With will and persistence they can be overcome.”

He said that the concern that private schools teachers might struggle in difficult schools was misplaced: “You have excellent teachers, many of whom are eager to play their part,” he said.

Calling his speech his “Lord Kitchener Moment” he told heads “your country needs you” before concluding:

“There is a perception that the independent sector only does its duty when push comes to shove. That it doesn’t really care about the educational world beyond its cloisters and quads and only reaches out when the Charity Commission, universities or government forces it to act. I think that’s unfair.

“Some of you are doing excellent work. But I can understand why inaction in other cases can be misconstrued as indifference.