A division has emerged in the Roman Catholic Church over whether or not Christians should vote for the Greens.

The Archbishop of Sydney, Cardinal George Pell, warned Catholic voters on the weekend to be wary of the Greens, describing them as "sweet camouflaged poison".

But other Catholic leaders disagree. They say it does not reflect well on the Church when a man of Cardinal Pell's position uses that kind of language.

The stoush between the Greens and the Australian Christian Lobby (ACL) started late last week when the ACL accused the party of refusing the scrutiny of Christian voters.

All major and minor parties were sent a questionnaire from the lobby group but the Greens refused to respond to 18 out of the 24 questions.

The ACL's managing director, Jim Wallace, says it was dishonest of the Greens to ignore the questions.

"Even the Sex Party answered honestly the questions - I don't agree with their positions, but at least they were honest enough to actually put their replies forward and respond today whereas the Greens weren't," he said.

"I don't support the Sex Party but I certainly don't support either a party that doesn't act honestly before the electorate."

The Greens say all their policies are clearly stated on their website.

But Cardinal Pell's weekend newspaper column slammed the Greens' so-called Stalinist roots.

He said the Greens were anti-Christian and opposed to the notion of family

"One wing of the Greens are like watermelons - green outside and red inside - a number were Stalinists supporting Soviet oppression," he said.

"We all accept the necessity of a healthy environment but Green policies are impractical and expensive which will not help the poor.

"For those who value our present way of life, the Greens are sweet camouflaged poison."

Mr Wallace agrees with the Archbishop of Sydney.

"I think that what he said there is simply illustrated by the fact that they've shown so much deception in the way that they've avoided showing their hands to Christians on a whole range of issues, such as euthanasia, abortion, prayer in Parliament, funding of schools, marriage, surrogacy... a whole range of issues," he said.

'Unfortunate language'

But Father Frank Brennan from the Public Policy Institute at the Australian Catholic University was not impressed with the article.

"I was surprised by the tenor of the remarks - the Christian lobby, of course, is a self-appointed group who, as they describe themselves, are as a lobby and they invoke how they would see the Christian gospels to be lived out in the community at large," he said.

"Cardinal Pell, of course, is in a different class. He's one of the respected leaders, a key bishop of the Australian Catholic church.

"I'm a member of the Catholic Church - most Australian Catholic bishops, of course, haven't used the sort of language that Cardinal Pell has used.

"I think it's unfortunate language. I don't think there's any need to label the Greens as being 'sweet camouflaged poison' or 'thoroughly anti-Christian'.

"I know some members of the Green Party, some of whom I think are thoroughly Christian and the idea that they're 'sweet camouflaged poison', I think that sort of language during an election campaign from a respected church leader, I don't think it does any of us any good, least of all our church."

Father Brennan says some Christians like the idea of a third party having the balance of power in the Senate instead of the government of the day controlling both houses.

He has suggested voters look for politicians of good character.

"Character is something more than religious faith, definitely those of us who are Christian would say that those who don't have religious faith, we would hope that there are other ways in which they could exhibit strong character," he said.

"But equally, it's got to be said, but not even Christians can claim that simply because they have faith, that they have good, strong and robust character."

Father Brennan says in future, if the Christian Lobby wants to mount such a rhetorical election campaign, bishops should offer a dignified distance and reticence.