Chief Minister Natasha Fyles’ office has defended senior political adviser Gerard Richardson’s dual roles as adviser to the NT Labor Government and co-owner of a company that lobbies for Tamboran Resources, which the Federal Greens have called “outrageous and alarming”.

The NT Independent revealed on Tuesday that Mr Richardson’s consultancy company Brookline Advisory is the registered lobbyist for Tamboran on the federal lobbyist register – a gas company with massive interests in the Beetaloo Basin – which was also given special considerations by the government for land at the Middle Arm industrial precinct to build a large LNG plant.

Independent teal Member of Parliament Monique Ryan earlier this week called for a full investigation into Ms Fyles’ office for the conflict of interest, saying “voters have the right to expect their politicians and their advisers make decisions in the public’s best interests, not their own”.

However, Ms Fyles’ office released a statement to the NT News on Thursday, stating that Mr Richardson had “provided assurances” the Fyles Government “would be [Brookline’s] only client in the NT”.

“Mr Richardson is a Territory resident and provides advisory work to the government,” the statement from an unnamed spokeswoman said.

“He has declared the nature of Brookline’s work for Tamboran.

“He does not do work for Tamboran and does not do any work for anyone based in the Northern Territory other than the government.”

Tamboran does not have any current interests in Australia outside of the Northern Territory. Its website states its “primary asset is its 1.9 million net acreage portfolio in the Beetaloo/McArthur Basin in the Northern Territory”.

The NT is the only jurisdiction in the country without a lobbyist register.

Greens Senate Leader Larissa Waters said Ms Fyles hiring a lobbyist as her senior adviser was harmful to democracy and the environment.

“It is outrageous for Mr Richardson to be in charge of political strategy for the Chief Minister of the Northern Territory, while [his company is] also lobbying for Tamboran Resources to unleash a carbon-bomb by fracking the Beetaloo Basin,” she said.

“It’s bad enough when we see ex-parliamentarians and senior staffers heading straight into a lobbying role after they leave office – but in the NT, the lobbyists appear to be on the parliamentary payroll.

“This isn’t just a back door into Parliament and influencing political decisions, it’s rolling out the red carpet for Tamboran to have all the information they need to get their way on Beetaloo.

“This is absolutely unacceptable and yet another case of poor decision-making from Chief Minister Fyles. The Northern Territory, democracy and the environment deserve better.”

Labor sources have told the NT Independent Mr Richardson would have access to Cabinet agendas and other documents in his role as senior adviser to the Chief Minister.

Ms Fyles and Mr Richardson have repeatedly refused to comment on his involvement at Cabinet meetings, including whether he had attended Cabinet meetings as Labor sources have claimed.

Ms Fyles came under intense criticism last month after the NT Independent revealed she had an undisclosed number of shares in gas giant Woodside Energy, which is currently scoping out a potential carbon capture and storage hub at Middle Arm.

After first defending the shares and defiantly claiming she was keeping them, she later moved to divest them after it was revealed she had breached the ministerial code of conduct by not divesting the 169 shares when she first became aware of them last year. It was also later revealed that Ms Fyles did not disclose that her husband worked in a senior role for Careflight – a company she has overseen awarding government contracts to worth tens of millions of dollars.

The issue of Mr Richardson, who was employed by Ms Fyles through Brookline earlier this year, was revealed the same week The Guardian reported on internal documents that showed the government altered its climate policy on new gas projects to suit the gas industry’s demands late last year without properly consulting any other stakeholders.

The NT News reported that Deputy Chief Minister Nicole Manison also defended Mr Richardson’s company operating as a lobbyist for the gas industry while he provided political advice to the Chief Minister as “absolutely appropriate”.

Leading national integrity expert Geoffrey Watson, director of the Centre for Public Integrity, told the NT Independent on Tuesday that he had “never seen such a comparably obvious conflict of interest” and struggled to understand “why anyone would think this is appropriate”.

Tamboran did not respond to the NT Independent’s questions, including why it hired Brookline Advisory as its lobbyist, if Brookline had commenced any works for the company before the November 8 date provided on the register and if the company had obtained any potential Cabinet-in-confidence material from Brookline relating to NT Government gas policy decisions.

ASIC records show Brookline Advisory is co-owned by Mr Richardson and Lidija Ivanovski – a former adviser to ex-chief minister Paul Henderson and the second-in-charge of Federal Labor’s 2022 election campaign.