The leading voice of the independent schools sector has resigned after two months after sparking controversy by criticising state schools.
Chris Parry left the Independent Schools Council (ISC), which represents 1200 private schools, by "mutual agreement" it has said.
This followed a meeting of leading public school heads on Wednesday.
The heads had expressed "deep concern" over his war-like view of relations between private and state schools.
Early last month he clashed with Barry Sheerman, the chair of the Commons schools committee, claiming failings in the state system made parents pay twice to send their children to school
He also used the phrases "Cold War" and "sectarian divide" to describe relations between state and independent schools.
We are an integral part of the education sector and desire cooperation with the state sector not conflict
Richard Cairns, head teacher Brighton College
The commission wants schools to prove their wider public benefit to justify their charitable status.
The statement from the ISC said: "Chris Parry has today, by mutual agreement, stepped down as chief executive of the Independent Schools Council.
"Although he was looking forward to making a difference in the sector, Chris has chosen to take up other opportunities that he has been offered."
The head of the independent Brighton College, Richard Cairns, said: "Mr Parry's lack of understanding of the needs and workings of the independent sector is frankly astonishing.
"The military metaphors were deeply unhelpful. We are an integral part of the education sector and desire cooperation with the state sector not conflict."
In his inaugural address to the ISC Mr Parry's presentation involved pictures of warships and tanks.
And the former rear admiral referred to the independent schools heads as his "subordinates".
Yesterday, about 25 of the heads of leading independent schools in the south east of England met and there was "unanimous deep concern" about Mr Parry, said Richard Cairns.
"His position was then untenable."
They reported their views directly to the ISC.
John Dunford, the leader of the Association of School and College Leaders - which includes independent and state school heads - said: "His resignation underlines the importance of mutual respect between independent and state schools and Chris Parry clearly crossed that line in a way his independent colleagues could not accept".
Mr Parry has not commented. A spokeswoman said Mr Parry and the ISC had agreed not to discuss his departure publicly.Matthew Burgess, the ISC's general counsel, has taken over as the organisation's acting chief executive.