MSPs accused them of failing to show leadership, questioned the reliability of their school board survey as a test of parental opinion and suggested they had helped to inflame the debate by failing to disassociate themselves from “scare stories” about gay lessons in schools.

David Hutchison, the association’s president, repeatedly advanced the defence that “my job is to represent my members: my own views are irrelevant”. Mr Hutchison said it was now up to the Government to reassure parents, although he did accept that Section 2A was “discriminatory”.

He also reminded MSPs that the association was not arguing for the legislation to remain on the statute book. Its demand was for parents to be consulted over what will take its place. He warned: “If the Government doesn’t consult parents on the draft guidelines, we will.”

John Waddell, who represents the SBA on the working group reviewing guidance on sex education, said that its work to date was “falling short” of what would satisfy parents. Mr Waddell is pressing the group to adopt the “traditional family values” David Blunkett, the Education Secretary, is set to introduce for England. Mr Hutchison said that would not preclude classroom discussion of homosexuality.

The new clause added to the Ethical Standards in Public Life Bill, the legislative vehicle for repealing Section 2A, simply requires local authorities to underline the importance of “stable family life” in dealing with children.

MSPs also heard from the Educational Institute of Scotland and the Scottish Parent Teacher Council, which both support the extension to sex education of clause 12 in the education Bill, which binds education authorities to “have regard to” ministerial guidance on raising standards.

All sides agreed there was no evidence of “inappropriate material” finding its way into schools before the advent of Section 2A but the campaign to retain it has so heightened parental fears that reassurance was now needed.