If the changes go ahead, 250,000 people, of which 27 per cent are Indigenous, will be represented by one lower house MP.
The Australian Electoral Commission announced on Thursday that the Northern Territory will lose one of its two lower house seats in the federal parliament.
Victoria will gain another electorate, increasing from 38 to 39 seats, while Western Australia will also lose one of its 16 seats.
The determination was finalised by the Australian Electoral Commissioner, Tom Rogers, who based the decision on the slow population growth of the NT and WA.
“The figures show the population has increased sufficiently to result in Victoria increasing its entitlement by one seat. At the same time, the determination of entitlement requires Western Australia and the Northern Territory to each decrease by one seat,” Mr Rogers said.
The decision to halve NT's allocation has received an angry response on Twitter, especially from members of the Indigenous community who say the decision means that they will lose their voice.
The Northern Territory has the highest proportion of Aboriginal and Torres Strait Islanders of any state or territory.
Labor has introduced a bill to the Senate, with the support of the Nationals Senators, including CLP Territory Senator Sam McMahon, to maintain the Northern Territory’s level of representation in the federal parliament.
The NT branch of the Labor Party has warned that "the Territory will be the most under-represented in Australia".
"If no action is taken, this means the Territory will see its representation in the House of Representatives halved, consisting of one, enormous electorate.
"If the changes decreasing the NT's lower house capacity to just one seat goes ahead, 250, 000 people of which almost 30 per cent are Indigenous, would be represented by one lower house MP."
The electorate of Solomon, held by Labor's Luke Gosling, covers Darwin and surrounds, while the division of Lingiari, represented by Labor's Warren Snowdon, covers the rest of the vast Territory.
Mr Gosling called for the NT's two seats to be guaranteed, similar to the arrangement which secures Tasmania's five seats, despite the state's small population.
"The Territory deserves fair representation in Canberra," he tweeted.
Labor Senator for the NT, Malarndirri McCarthy, is encouraging Territorians to make a submission.
"This is not good enough. This is a fight against the continued erosion of our Territory voices in Canberra," Senator McCarthy tweeted.
Mr Rogers said the Electoral Commission was scheduled to meet on 14 July to direct the commencement of federal redistribution processes in Victoria and WA.