The Mercury reports that Archbishop Doyle outlined the policy when he confirmed plans for a new $12 million Catholic high school for Kingston.
He said the new school, the St Aloysius Catholic College, would be the first to introduce the policy to have at least 75 per cent of baptised Catholic students.
He said about 40 per cent of students in Tasmanian Catholic schools were not Catholic.
Archbishop Doyle said his policy would ensure a "very strong Catholic ethos and vision" in schools.
The move will require an exemption under Tasmania's Anti-Discrimination Act, which the State Government will consider later this year.
The St Aloysius Catholic College will open in 2009.
It will be built at Huntingfield on church-owned vacant land, near the Tarremah Steiner School and will be an expansion of the St Aloysius Primary School at Kingston Beach.
A "green building" is proposed, using solar power and efficient water use.
The co-educational college will have a strong emphasis on performing arts.
Archbishop Doyle said his 75 per cent Catholic policy would be slowly rolled out across the state.
"St Aloysius Primary School is already aware of this policy, so enrolments will start to reflect that," he said.
"It will be a question of preference, if there had to be that difficult choice between one (student) or the other (non-catholic student).
"I think now I have taken this stand with this school, I will extend the policy wider."
Catholic Education deputy director Anthony Morgan said the school would cater to students who lived in the South and travelled into Hobart to attend Catholic schools.
He said the nearest co-ed Catholic school to Kingston, Sacred Heart College, was turning students away.
The nearest Catholic boys high school, St Virgils at Austins Ferry, had taken on extra students to cope with demand.
The new school will take students from Year 7 and will eventually grow to 360 students.
Archbishop Doyle said Kingston was an area of "great growth" and could absorb the new Catholic school and the proposed $30 million state school.
He said the next Catholic school could be built in Launceston, where there was only one Catholic college.
"The establishment of this new Catholic College, which will be an extension of the existing St Aloysius Primary School, will be a wonderful opportunity to provide Catholic Education at the secondary level to the growing number of students who live in the Kingborough area," Archbishop Doyle said in a statement.
Catholic bias to new school plan (The Mercury, 31/5/07)
Growth area to get new Catholic high school (ABC News, 30/5/07)
New education choice for Catholic families (Media Release, Hobart Archdiocese, 30/5/07)
LINKS (not necessarily endorsed by Church Resources)
Archdiocese of Hobart
Federal and state anti-discrimination law
Tas church presses for school anti-discrimination exemption (CathNews, 30/4/07)