The public sector teachers' union has urged the ACT government to block proposals for three faith-based schools to build new campuses in Canberra's north and west.
In its submission to the government, the Australian Education Union says the new Christian and Islamic schools in Belconnen and the new Molonglo suburb of Wright would divert students from surrounding public schools and might result in the closure of established public schools in Belconnen.
The union is also arguing the applications from the religious organisations are lacking in detail and have failed to make their cases the new schools are needed.
Seventh-day Adventist School Canberra Christian College wants to build a campus in Wright while its multi-denominational counterpart Brindabella Christian College wants to take over the old Charnwood High School.
The union is dismissive of the college's application for Molonglo.
''The application includes little evidence of community demand for a new Molonglo campus,'' the union's submission reads.
''No expressions of interest from prospective students/families are provided.
''The only evidence provided is in the form of supportive letters from Christian Schools Australia, Adventist Schools Australia, Adventist Schools Greater Sydney, three parents of students enrolled at the existing campus and a former student.
''No evidence is provided regarding community consultation and there is no mention of what existing schools prospective students may come from.''
The union says the At Taqwa proposal, which is supported by expressions of interest from the parents of 116 local children, would be better moved to Gungahlin where schools are at or close to capacity.
''If the At Taqwa School is to be located in Gungahlin, the impact on existing government and private schools would be much lower,'' the union writes.
''In fact, the application makes plain that 116 students would leave surrounding public schools in the [Belconnen] region to attend the proposed school.''
But a religious schools' peak body says the union is motivated by its traditional enmity for religious schooling.
Christian Schools Australia chief executive officer Stephen O'Doherty says the three schools are reacting to demand from ACT parents for faith-based schooling.
''Recent history has shown there is strong demand for faith-based schools in Canberra and if I could speak for Brindabella, Brindabella has demonstrated a strong commitment to Charnwood,'' Mr O'Doherty said.
''It believes that school would be a great service to the community and they're looking forward to opening there as soon as possible.'' Mr O'Doherty said his organisation rejected the union's argument religious and public schooling could not co-exist in the suburbs.
''The union is a long-standing opponent of a sort of faith-based schooling and it's submission should be read with that in mind.
''The AEU [the union] is arguing that the school hasn't demonstrated a demand therefore there's no need for the school but they're also arguing that if the school were to be opened, it would cause problems for the nearby public school. Both those two things can't be true.''