And Peter Ryerson, education chairman, criticised the York-based body for its choice of messenger to deliver the proposals - FAS member Sir Edward Lister, leader of Wandsworth, the Conservatives' favourite borough.
"Why should he make decisions over Hillingdon?" asked Mr Ryerson. "It really does grate."
Roger Witts, FAS head of communications, countered: "Sir Edward was neither selected at random nor deliberately. He was the obvious person to represent the board's feelings. He is chair of the FAS planning committee."
Feelings run high in Hillingdon, where the council has had to close three schools over the past three years. Under the FAS proposals, the LEA claimed popular schools in the borough would be allowed to expand despite nearby ones having surplus places. None of the three local authority schools would be allowed to take in extra pupils.
Mr Ryerson feared the proposals, which concentrate on admission numbers, would create schools with eight forms of entry and up to 1,500 pupils.
He suggested re-opening Barn Hill, a school in the south of the borough which closed three years ago, and said: "While the authority recognises the apparent generosity of this model, I am concerned that it flouts the Department for Education rules in a way that no local authority would be allowed to do and that it could result in Hillingdon once again being in the position of having surplus places in the system as defined by DFE criteria.
"Having recently been through the pain of school closures, it would be a matter of great regret for this authority if these proposals had the knock-on effect of further closures."
Glenys Andrew, education director, added: "If we put forward these proposals using the DFE criteria of basic need, we would only be eligible for about half of what the FAS is proposing."
Under the FAS proposals six GM schools - Douay Martyrs, Haydon, Mellow Lane, Queensmead, Swakesleys and Vyners - would expand, starting in September 1998. The move is designed to combat a particularly acute shortage of places in Hillingdon, where 12 out of the 15 secondaries have opted out.
The FAS did not put forward plans to re-open or build a new school as it did not believe these were "real options" at the moment, but Roger Witts said: "Nothing is set in stone."
He added: "We are aware of the DFE guidelines. We are not immune to them - no one is - but we are trying to run with the grain of the schools themselves. Four out of the six schools already had plans to expand."
The consultation period on the proposals closes on November 30.