The Northern Territory Government is under pressure to give a detailed breakdown of the $506 million price tag attached to the long-term lease of Darwin Port to a Chinese company, after questions were raised about a possible multi-million dollar shortfall.

Key points: NT Government says it has received $506 million for 99-year lease of Darwin Port

NT Government says it has received $506 million for 99-year lease of Darwin Port Port Lease agreement shows lease premium was $391 million, plus stamp duty of $23 million

Port Lease agreement shows lease premium was $391 million, plus stamp duty of $23 million Government under pressure to explain sale price tag

The Government announced in October that Landbridge Group, owned by Chinese billionaire Ye Cheng, had been awarded a 99-year lease.

At the time the Government said the deal was worth $506 million and has since told the ABC it has received that money.

But the Port Lease agreement tabled to the Senate showed the lease premium was about $391 million, $115 million less than the figure initially stated, plus stamp duty to the value of $23 million.

"Adam Giles needs to explain this to Territorians," Labor's Natasha Fyles said.

"He sold the port off without a mandate, he needs to explain to Territorians exactly how much he sold the port for.

"He's claimed one figure, he needs to show the documents."

A statement from the NT Government said it had received the full amount originally quoted.

"The revenue received by the Northern Territory for the Port lease was $506 million," the statement said.

"Included in that figure was an amount agreed between the Northern Territory Revenue Office and Landbridge to be the lease amount, along with other non-lease costs, such as stamp duty.

"We received $506 million for the long-term lease arrangement, and regardless of how it is split, it is all income for the Northern Territory."

Despite its opposition to the deal, Labor has said it would honour the agreement if it forms government.

"If there's a commercial agreement in place we would seek the advice of the public service about what best to do," Ms Fyles said.

"But as we understand the port has been leased for 99 years, there's a commercial agreement in place, and Territory Labor would need to honour that if elected to government."

Chief Minister Adam Giles was unavailable for interview.