New rules governing who can take the British throne should put an end to royal "religious discrimination" against Catholics, the Green Party says.
British Prime Minister David Cameron needs the assent of 15 Commonwealth countries including New Zealand for a proposed change to royal succession law.
It would scrap a ban on royals who marry Roman Catholics taking the throne and give women the same rights of succession as men.
However, any royal professing Roman Catholic faith themselves would still be barred from the throne.
Retiring Green MP Keith Locke said that amounts to religious discrimination.
He urged Government to hold out on passing the bill until it ends all prohibition against Catholics.
"To do otherwise makes a mockery of our Human Rights Act, which prevents discrimination on religious grounds."
Under the Act of Supremacy passed by King Henry 8 in 1534, the British monarch automatically becomes supreme governor of the Anglican Church.
Mr Cameron told the BBC any change to the ban on monarchs being Roman Catholic would interfere with that their place at the head of the church.
But Mr Locke said that was less important than the human rights of Catholics.
"We should ask Mr Cameron to be a little bolder and remove all discrimination against Catholics.
"If that means the monarch can no longer automatically be head of the British Anglican Church, so be it."
- HERALD ONLINE