The Australian Education Union has criticised a proposal to reintroduce religious education to the Victorian curriculum, saying instruction should take place outside school hours.

The state opposition leader, Matthew Guy, announced the plan at an Australian Christian Lobby election forum on Saturday where he spoke alongside the Rev Peter Hastie, the father of federal conservative Liberal MP Andrew Hastie.

The Andrews government removed religious instruction from the state curriculum in 2015 in favour of a program on respectful relationships, which is intended to help recognise and prevent family violence. The lessons also focus on global cultures and faiths and promote respect for diversity.

Schools are still able to provide 30-minute religious instruction classes, which are usually delivered by a volunteer, but the classes have to be outside regular classroom hours on an opt-in – rather than opt-out – model.

AEU’s Victoria president, Meredith Peace, said religious instruction had no place in “free and secular” public schools and accused Guy of pandering to the conservative wing of the Liberal party.

“We have not heard from Matthew Guy about his plan to fund public education in Victoria and that, I think, is what parents want to know about, not his plan to accede to the rightwing conservative voices within the Liberal party and come up with another peripheral policy,” Peace told Guardian Australia.

She said the AEU supported general education about religions in public classrooms but not instruction about any one particular religion.

“If people want their child to be educated in religion then they are able to do that in their own time,” she said. “Our public schools are not the place for that.”

According to Fairfax Media, Guy told the forum that religious instruction in schools was “very important”.

“A government I lead will always believe that you determine the values by which you raise your children, not the education department,” he said.

If it wins power in next month’s state election, the opposition has also pledged to abolish the Safe Schools program, a move that the AEU also opposes.

A survey commissioned by the AEU in July of 500 parents of school-age children and 500 members of the general population found that 46% supported funding the respectful relationships curriculum, which was a recommendation of the royal commission into family violence, while 15% were opposed.

That same survey found that 44% of respondents opposed scrapping Safe Schools, while 27% supported getting rid of it and 28% were undecided.

When Labor ditched in-class religious instruction in 2015 the education minister, James Merlino, said just 20% of primary school students took part in the weekly classes while the remaining 80% had opted-out.

“You can’t have 20% of school kids undertaking special religious education, while the other children are not getting teaching or learning, during precious curriculum time,” he said.

In a statement on Tuesday, Merlino said that removing religious instruction from the curriculum was a “common sense change.”

“The bottom line is that extracurricular programs should not interfere with class time when teachers and students should be focused on the core curriculum,” he said.

The opposition has been contacted for comment.