The Equality and Human Rights Commission has released a new guideline for the school and local councils stating that they could be guilty of discrimination against women if they hold parent or meetings in the evening.
According to the Commission, the timing of such events could mean some women are unable to attend - a disadvantage that exists because of their domestic duties.
The guidelines from the quango were in a code of practice explaining the new Equality Act, which was passed just before the election and championed by Labour's deputy leader Harriet Harman.
It states a local council could be hit by a legal claim if, when it holds consultation meetings on a weekday evening, "it discovers fewer women than men attend".
A woman could make a case on the basis "that this is because some women cannot come because of childcare responsibilities".
"This is enough to demonstrate disadvantage," it said.
"She does not have to show the absence of women is attributable in particular cases to childcare responsibilities."
"It is extraordinarily idiotic when we need to be encouraging people to come together," the Daily Mail quoted Graham Stuart, Tory chairman of the Commons education committee, as saying.
"The last thing we need is to put the fear of God into people who want to hold a meeting in the evening," Stuart added.
A commission spokesman said, "It's sensible for a public body to think about who it wants to consult and what time of day those people might be available."