They are to tell ministers that increased delegation within local management is the reason why more schools are not opting out. The criticism from the nationally-recognised Grant-Maintained Schools Advisory Committee comes as ministers prepare for 95 per cent delegation.
The committee warns: "The Government should be aware that its headlong move towards greater delegation is a major reason why recruitment to GM status has faltered."
It said schools had preferred "the safer, but less effective route of staying wedded to the local education authority".
Ministers have maintained that LM schools would be more likely to opt out if they were delegated even more of their budget as then there would be only a short step between the two sectors. However, their reasoning appears to have been mistaken.
Since the beginning of the year 10 secondary schools have voted to go GM, 12 said no. In the primary sector more schools voted to opt out than not - 28 compared to 22.
Levels of local authority delegation currently range between 95.8 per cent in Dudley to 85.1 in the Isles of Scilly. Ministers signalled their intention to increase delegation to 95 per cent in the White Paper Self Government for Schools.
The GMSAC's response said: "If greater delegation is to proceed, the GM sector must receive further incentives to ensure its future."
Chairman Pauline Latham said it wanted more capital funds, extra cash to reflect the responsibilities undertaken by GM heads and their senior management teams and a national funding formula for all schools.
"We feel that we do a better job that LM schools and that should be recognised in our funding," said Mrs Latham, a governor at Ecclesbourne School, Derby.
GM schools believe they are at substantial disadvantage in the way capital grants are calculated and challenge Government claims that a national funding formula was problematic because it would produce winners and losers.
"There are winners and losers with the present funding mechanisms," said the GMSAC.