Adam Giles has been dumped as the Northern Territory's chief minister after a late-night leadership spill.

The Primary Industries Minister and Member for Katherine, Willem Westra van Holthe, 52, held a brief press conference at 1:00am to announce he had seized control.

The successful coup came after a phone hook-up late on Monday, the same day several of Mr Giles's Country Liberals colleagues pledged their support for him as leader.

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The ABC understands the vote was split nine votes to five.

The coup came after reports on Monday that Mr Giles narrowly avoided a leadership challenge last week amid ongoing concerns about his leadership style.

One minister told the ABC's AM program the fallout from the Queensland election had prompted the challenge because it exacerbated concerns the Territory Government was seen as arrogant and could lose office after one term.

Attorney-General John Elferink is the new deputy, replacing Peter Chandler.

Discontent around for some time, says new leader

For some time several of Mr Giles's colleagues had been unhappy with his leadership, saying he interfered in their portfolios and accusing him of having a dictatorial leadership style.

Some were also upset by a recent Cabinet reshuffle, saying it was motivated by a desire to shore up support for Mr Giles rather than a desire to choose the best ministers for the job.

In his hastily arranged press conference, former policeman Mr Westra van Holthe said "tonight was no particularly special night" when asked what had triggered the overturning of Mr Giles's rule.

He said there had been "discontent with the direction of government" which had "been around some time".

Speaking from a prepared statement, Mr Westra van Holthe said the Government "could have done things better in the past".

"Under my leadership, this government will be more consultative with Territorians and engage with them before we make important and crucial decisions to the future of the Territory," he said.

Mr Westra van Holthe will be the Country Liberals' third leader since the party won government two-and-a-half years ago.

He said his Government wanted to provide "stability and confidence for all Territorians, especially our public service".

"We acknowledge that we must work more closely with the community as we move forward and make the Territory a better place to live," he said.

Mr Westra van Holthe thanked Mr Giles "for his time as chief minister".

When asked if he would explain why the party had dumped Mr Giles, he said more information would be released today.

Willem Westra van Holthe, flanked by John Elferink, speaks at an extraordinary 1:00am press conference to announce the dumping of former NT chief minister Adam Giles. ( ABC News: Sara Everingham )

Pressed on the matter, Mr Westra van Holthe said he would be "far more consultative with the people of the NT ... I'll have faith in the ministers with whom I am working".

Mr Westra van Holthe described himself as an "honest, hard-working man who wants to deliver the very best results I can for the Territory and for Territorians".

After speaking for three minutes, Mr Westra van Holthe took three questions before he called an end to the press conference and walked out.

Mr Elferink remained silent throughout.

Mr Westra van Holthe is the third CLP chief minister since the party came to power in the Northern Territory in August 2012.

Giles 'has my support', says Lambley on day of coup

There had also been concern about Mr Giles's handling of the scandal surrounding former police commissioner John McRoberts, his championing of the sale of the Territory Insurance Office and his ability to communicate the Government's strategy to the public.

Who is Adam Giles? Adam Giles was Australia's first Indigenous head of government. The 41-year-old father of one is the Member for Braitling. He was born in the Blue Mountains region of NSW and studied accounting and real estate. He worked in public housing management for the Aboriginal and Torres Strait Islander Commission, then moved to Canberra and worked for the Department of the PM. In 2004 he stood as the Liberal candidate for the ACT electorate of Fraser. He later settled in Alice Springs, and stood as a CLP candidate for Lingiari in 2007. He lost, but was elected to the seat of Braitling in the 2008 Territory election. He became Transport Minister after the 2012 election. He had recently faced concerns about his leadership style, his personal judgement, his communication with the public and his handling of the scandal surrounding former Police Commissioner John McRoberts.

Yesterday Mr Giles acknowledged he had heard some leadership rumblings, but said he believed he still had the support of his colleagues and defended his record.

"I think it's good that everyone in Parliament wants to be the chief minister and wants to be able to put forward their vision, their view about how to take the Territory forward into the future," he said.

On the day of Mr Westra van Holthe's trumping of Mr Giles, then-deputy chief minister Mr Chandler said: "Look, we have a Chief Minister, we only need one Chief Minister. We have one, we don't need another one."

At a Darwin school to speak to students about leadership, Mr Chandler said Mr Giles "absolutely" had his full support.

Speaking in the afternoon in the lead-up to the coup, Corrections Minister Robyn Lambley said the weekend's devastating Queensland election result for the Liberal National Party had not gone unnoticed.

"Adam Giles has my support, but it is a time of reflection. I think what we've all taken away from the Queensland election is that nothing can be taken for granted and perception is everything," Ms Lambley said.

Sweet revenge for Mills, the man Giles ousted

Mr Giles, 41, secured the NT's top job in March 2013 from Terry Mills, who was in Japan on a trade mission and learnt by telephone he had been rolled by Mr Giles and close Giles ally, Dave Tollner.

Afterwards, Mr Giles rebuffed media descriptions of the episode as a coup.

Mr Giles, who had stood for election in the ACT in 2004, became Australia's first Indigenous head of government.

Terry Mills, the man rolled by Adam Giles as NT chief minister in 2013, retweeted an ABC tweet about Mr Giles suffering the same fate. ( Supplied )

Mr Mills, who led the CLP back into office in August 2012 after 11 years in opposition, resigned from politics in February 2014 to take a job in Indonesia as a trade envoy.

Soon after the news broke of Mr Giles being dumped on Monday, Mr Mills retweeted the news and a photo of him laughing.

Less than an hour after Monday's coup, Mr Giles's Wikipedia page had been amended and Mr Westra van Holthe had been installed as the new leader.

The tumultuous events round off Mr Giles's reign over a troubled CLP, which has been split by personal rifts and controversies since it won government.