A lobby group is planning legal action against Australia’s government, saying a 2001 law change was discriminatory and meant hundreds of thousands of expat New Zealanders were struggling to access healthcare, welfare and tertiary education.

David Faulkner from the lobby group Kiwis in Australia said about 250,000 New Zealanders had been affected by the legislative change, and Māori New Zealanders were disproportionately affected.

“New Zealanders are now the only group indefinitely residing in Australia that cannot apply for citizenship after the usual four years of residence. Labor, the Greens, and even Pauline Hanson’s One Nation all have policies to change this situation, but the Coalition [government] has remained intransigent – so legal action is the only realistic option at this time,” Faulkner said.

“The basis for the case is that the 2001 Australian citizenship law changes are unconstitutional as they unreasonably deny the right to vote to the affected cohort, and also constitute unlawful race discrimination.”

According to academic research published in the Conversation, Māori New Zealanders are disproportionately affected by the 2001 change.

“Of the 146,000 New Zealand-born migrants who arrived in Australia between 2002 and 2011, only 8.4% had acquired Australian citizenship by 2016. As a subset of this, New Zealand-born Māori are particularly disadvantaged, with a take-up rate of just under 3%.”

The authors noted that “since 2001, the access of New Zealanders to Australian citizenship has almost collapsed. This is especially so for New Zealand-born Māori, who are less likely to be able to meet the skills requirements or the cost of a permanent visa.”

Faulkner said other groups adversely affected were New Zealand women trying to escape domestic violence situations in Australia. He said they were being denied “proper support and shelter” by the state. Disabled children born to New Zealand parents also struggle, because they are unable to access disability support services.

Since the lobby group announced its intention to pursue legal action in the federal or high court, more than 700 people have been in touch pledging their support, and some have already started donating towards costs.

“We anticipate that the end number joining the action could well run into many thousands. Such a large number would mean that the action could be funded via a relatively small outlay from each participant,” Faulkner said. The group is in the process of selecting a legal firm to represent the civil suit.

New Zealand prime ministers have previously raised the issue of New Zealanders in Australia, but with no success.

Australians living in New Zealand have access to welfare support, tertiary education and comprehensive free healthcare.