Until now the Holy Ghost Roman Catholic Primary School in southwest London's Wandsworth asked people to complete a form that had spaces only for the names of the "mother/guardian" and "father/guardian".
A local parent referred the school to the schools adjudicator, arguing that the use of "mother" and "father" discriminated against "separated, step and gay parents", The Sunday Times reports.
In a recent ruling by adjudicator Peter Goringe, the Catholic primary school was found to be in breach of the UK government's school admissions code because of its use of the traditional terms on a form that families fill in to supply evidence of church attendance.
The UK's Catholic Education Service is now drawing up a form that can be used by its 2,230 schools across England and Wales that instead refers to "the family".
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Hundreds of schools have already replaced the titles with "parent 1" and "parent 2" or "parent/s".
"We expect all Catholic schools to comply with the admissions code," the service said in a statement.
Chris McGovern, chair of the Campaign for Real Education, said: "To ensure fairness, we should not be placing 'mother' and 'father' on a list of forbidden words. We should, instead, be accommodating these cherished foundation stones of our civilisation within the admissions system.
"The decision to remove them is profoundly undemocratic and illiberal and is a capitulation to a form of politically correct fascism".