Parents with children at Christian schools are being urged to consider the protection of religious rights when they cast their vote on Saturday in the federal election described as "the most critical for religious freedom in living memory".

Christian Schools Australia has taken the unprecedented step of urging parents with children at its schools around the country to vote according to their religious values.

Christian leaders have written to Bill Shorten and Scott Morrison seeking their commitment to protect religious beliefs. Credit:Alex Ellinghausen, AAP

A flyer sent to parents does not tell them explicitly how to vote, but says Labor has indicated it would amend the Sex Discrimination Act to remove exemptions that permit religious schools to discrimate against students and staff. It says these exemptions protect what schools can teach and their ability to hire staff with shared religious values and beliefs.

It also says the Greens have threatened the ability of schools to employ staff with shared beliefs, while the Liberal Party has said it would protect the right to freedom of religion and rights of equality and non-discrimination in law.