The union's general secretary, John Quessy, said the approved strike action was the result of a frustrating negotiation style used by Catholic school employers and the proposals that had been put, which he said were "disrespectful and disgusting".

The Archdiocese of Canberra and Goulburn's Canberra schools include St Francis Xavier College, Merici and Mackillop College as well as Catholic schools in Goulburn, Queanbeyan, Cooma, Gundagai, Young, and West Wyalong.

Mr Quessy said schools within the ACT were expected to strike on Tuesday while those in NSW, including Goulburn and Queanbeyan, held strike action on Monday.

"The strike action is likely to affect around 650 staff and 31 schools in the ACT, according to the number of people who responded to ballot papers lodged with the Fair Work Commission," he said.

"Altogether, we expect at least 1000 teachers and staff to strike on Monday and Tuesday across the entire Canberra and Goulburn Diocese."

Mr Quessy said teachers and staff were frustrated by the potential for "an unfair distribution of resources" with employers hoping to negotiate with individual schools rather than as a collective.

"What they seem to want to do is negotiate everything on an individual level at a school and that's unsatisfactory for our members who don't want to see their conditions determined by what postcode they live in," he said.

The Archdiocese of Canberra and Goulburn's Catholic Education Office director, Moira Najdecki, said the strike was premature and unhelpful to ongoing negotiations.

"While we support the right of staff to take industrial action, to do so now is premature and does not do justice to the consultation process that's taking place," she said.

"We're talking with and listening to staff in a number of ways and we're confident we will reach an agreement that staff will support."

Ms Najdecki said Catholic school employers released a draft enterprise agreement on April 7 covering the majority of staff working in Catholic schools.

She described the proposal as "a new, contemporary agreement which presents a range of ideas about how schools can better support 21st century teaching and learning".

Catholic Commission for Employment Relations executive director Tony Farley has previously called on the union to "stop misleading Catholic schools into believing their conditions are under threat".

"From the very beginning Catholic employers have told the union that everything they have proposed is negotiable – we've never said any of our proposals are take it or leave it," he said.

Mr Farley has said the only winners from industrial action in Catholic schools were the union officials who have encouraged it.

"The union knows that an agreement that everyone supports will come from continuing the discussions we're already having," he said.

Ms Najdecki said more negotiation meetings were scheduled with the union and employers hoped to present a comprehensive proposal on October 1.