The Scottish Parent Councils Association, formerly the Scottish School Board Association, has seen its number of members drop from 2,500 to 300.
That has happened against uncertainty over whether the SPCA and the country's other main parent organisation, the Scottish Parent Teacher Council, will agree to form a single national body. The SPTC's membership has increased from 1,450 to 2,100 since last summer.
The SPCA held its first national conference at the weekend, where vice-president Donald Gunn MacDonald rallied delegates by warning that falling membership meant the organisation would "cease to be", unless members become "dragons and roar our fiery breath".
Failure to establish a national body soon, he added, would leave a "vacuum" that could mean "disaster" for Scottish education.
The SPCA believes parents need a new national body to compare good practice in different parts of the country. Secretary Henry Paul said that, at present, even working out whom to contact "takes ages and saps your will to live".
There was widespread agreement that the Government should take more of a lead, rather than leaving it up to education authorities to feed back local thoughts on the formation of a national body.
"I do have an idea that they actually don't want a national body and that's why they keep saying it's up to you to get on with it - because we're not going to get on with it, because we're not skilled enough to do it," said Wilma Miller, of Dumfries High Parent Council.
Jennifer Wallace, policy manager of the Scottish Consumer Council, argued that there could be a conflict of interest, since authorities making big education cuts, such as Aberdeen City Council, might not want strong parent councils.
Lorraine Sanda, national parental involvement co-ordinator at Learning and Teaching Scotland and a late substitute speaker for Schools Minister Maureen Watt, said: "I have no sense whatsoever that the Scottish Government does not want a national parent body."
She told The TESS, however: "It is for parents and parent councils to agree and drive forward any moves to set up a national body - it is not for government to do that. We have not yet reached the stage where parent councils feel they need a national body. They need time to decide for themselves."
That view was effectively endorsed by SPTC's development manager Judith Gillespie, who said parent councils had more important issues to address - such as school budget cuts in Aberdeen - and had co-ordinated impressive campaigns without a national body.
A Scottish Government spokeswoman said: "Feedback suggests that parents' immediate focus is on taking the time to make sure that parent councils are working effectively at local level, but we will continue to work and listen to all stakeholders, including the two national bodies, SPCA and SPTC."
Under the Parental Involvement Act 2006, parent councils came into being last August and school boards were consigned to the past. Delegates heard that 90 per cent of schools now had parent councils.