The announcement comes just months after the government declared it was seeking to balance their books.

Opposition Leader Gary Higgins is urging the Gunner Government to front the public about where the additional funds have come from.

"The Territory is flat broke through the Gunner Government's financial mismanagement, and now they've somehow found an additional $50 million to spend," Mr Higgins said.

"Territorians deserve to know where the new money has come from because we know they cannot be trusted when it comes to taxpayers' dollars."

In Katherine, the expansion of walking tracks at Nitmiluk National Park are underway as part of the initial investment.

To be spent over two years, the funding is expected to support events and festivals, bringing more people to the Territory every year.

As part of the second investment, an extra $15.1 million over two years will go towards enhancing visitor experiences in parks across the NT to support tourism operators and improve visitor experiences.

Major events and community festivals will see an extra $20 million and $27.7 million will be spent promoting the Territory nationally and internationally.

Chief Minister Michael Gunner said the second big investment will create local jobs by "supporting and growing our valuable tourism industry".

"More investment in tourism and events means more money into the Territory and that's good for local business."

According to the NT Government, the initial investment of $53.74 million in tourism infrastructure saw increases in holiday visitors and business event travellers.

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"TURBO1 put us back in the game in terms of tourism. TURBO2 will build on the success of that investment," Minister for Tourism, Sport and Culture, Lauren Moss said.

"We exceeded our TURBO1 holiday visitor target with 57,000 extra holiday bookings injecting an estimated $70 million-plus into the economy, which continues to grow.

"These are holiday visitors that are coming as a direct result of our Turbocharging Tourism investment.

"TURBO2 demonstrates our ongoing commitment to the tourism industry and will keep the momentum going from TURBO1."

Mr Higgins said the Opposition supported increased investment in tourism as long as it was done sensibly.

"Tourism is the single biggest private sector employer in the Northern Territory, and we support investing in domestic and international marketing," he said.

"But the Gunner Government has not proven it is spending wisely on anything. They trot out sceptical tourism figures as gospel and yet we're still hearing stories from established tourist and hospitality operators about the lack of visitors.

"What KPIs exist on the government's investments? What evaluations do they have in place to ensure they are spending wisely and strategically for this vital industry?"

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