The Animal Justice Party - which secured the ideal ''A'' spot on the ACT Senate ballot paper - has placed the Greens last on its preference list.

ACT Greens MLA Shane Rattenbury, who is the Minister for Territory and Municipal Services, oversaw the shooting deaths of about 1450 kangaroos last month to protect rare grasslands from overgrazing.

The Greens' lead Senate candidate, Simon Sheikh, said on Sunday the Animal Justice Party's ''silly decision'' was disappointing.

''Many of the party's supporters have found out about this and told me they are deeply disappointed.''

Yet the fledgling party's national campaign director, Willow Sloane, said the Greens had betrayed voters and must be sent a strong message.

''Mr Rattenbury signed off on the murder of up to 1600 kangaroos, despite extremely credible scientific evidence showing that a no-kill alternative was [preferable] and also far cheaper for taxpayers,'' she said.

Her party was right to be ''totally uncompromising'', she said.

''Until now, people concerned by the treatment of animals usually voted for the Greens,'' she said.

''They were probably just as shocked as us by what we saw last month: their blatant disregard, their lack of compassion and their lack of ethics.''

Mr Sheikh said Canberrans should ''reject the preferences that parties tell them'' and decide for themselves whom to preference.

He was proud of his record on animal rights in his former role as national director of GetUp! - which campaigned to ban live exports.

''I worked alongside the leaders of the animal rights movement in Australia and I'm convinced voters will realise the Greens are the party best placed to champion these issues,'' Mr Sheikh said.

After last month's cull, Mr Rattenbury said he wanted to explore alternatives in future, such as tranquilising and moving kangaroos to other parts of the ACT.

Yet Animal Justice Party ACT candidate Marcus Fillinger, an air force marksman who also runs an animal shelter, dismissed the minister's change of heart as a late attempt to win preferences.

''[The Greens] wanted to talk preferences while kangaroos were getting their heads blown off,'' Mr Fillinger said. ''It's a dirty, dirty game.

''When Mr Rattenbury is rubber-stamping a permit to kill, I take it personally.''

In Senate elections, most voters - about three in four in the ACT - take the simpler option of voting ''above the line''. The party that wins an above-the-line vote gets to decide how these voters' preferences flow.

When choosing which of the larger parties to favour, the Animal Justice Party settled on Labor, the Liberals and then the Greens. The Bullet Train for Australia Party opted for the Greens, Labor then the Liberals.

However, the Stable Population Party split its vote three ways, giving the three larger parties an equal share of preferences.