The world heritage-listed Kakadu National Park will be expanded to include thousands of hectares of ecologically sensitive land that contains uranium worth billions of dollars.

In a generous act, the Aboriginal traditional owner, Jeffrey Lee, has offered the land to the federal government so that it can become part of Kakadu, where he works as a ranger.

Mr Lee, the shy sole member of the Djok clan and senior custodian of the land known as Koongarra, could have become one of Australia's richest men if he had allowed the French energy giant Areva to extract 14,000 tonnes of uranium from its mineral lease in the area.

"I'm not interested in money. I've got a job. I can buy tucker; I can go fishing and hunting. That's all that matters to me," Mr Lee told the Herald in a rare interview in 2007.

The Northern Land Council, an organisation that represents Aboriginal groups in northern Australia, has written to the federal Environment Minister, Peter Garrett, offering the land on behalf of Mr Lee, the Herald has learnt. For years the pro-mining council delayed passing on the offer to the government as Areva held out hopes of extracting the uranium from its 12.5-square-kilometre lease.

But despite what Mr Lee, 39, described as "enormous pressure" on him "for a long time" he refused to be swayed in his determination to see the land become part of Kakadu.

"There are sacred sites, there are burial sites and there are other special places out there which are my responsibility to look after," Mr Lee said in 2007. "I'm not interested in white people offering me this or that … it doesn't mean a thing," he said.

The Koongarra deposit is only three kilometres from Nourlangie Rock, one of the most visited attractions in Kakadu.

According to Aboriginal beliefs, the land includes places where the rainbow serpent entered the ground, a giant blue-tongue lizard still lurks and should not be disturbed, and art that was painted on rocks hundreds, perhaps tens of thousands of years ago.

The Australian Conservation Foundation - a long-time critic of uranium mining - said the government should now move quickly to incorporate the land into Kakadu. ''Jeffrey Lee has put country and culture ahead of personal profit and his vision means this magnificent place will be protected for all people and all time,'' said the foundation's nuclear campaigner, Dave Sweeney.

The federal government must go through a legal process, including seeking a response from Areva, before moving to incorporate Koongarra into Kakadu. But Mr Garrett told theHerald the opportunity to include the land into Kakadu ''is clearly one that I would be keen to see realised''.

''While there are important questions of indigenous rights and natural justice that need to be worked through, this is a once-in-a-generation opportunity that I would naturally encourage,'' Mr Garrett said.

Areva executives in Australia did not return calls from the Herald. The blocking of the mine comes five years after a federal takeover of uranium mining from the Northern Territory Labor government that was supposed to boost uranium mining.

But the move is in tatters, with mining companies struggling to extract tens of billions of dollars worth of northern Australia's known uranium deposits because of the concerns of indigenous traditional owners about the impact.

The Mirarr traditional owners are opposing a massive expansion of the controversial Ranger uranium mine because of concerns about outdated procedures to protect the environment.

The Herald revealed this week that millions of litres of radioactive water have flowed from the mine into Kakadu.

Ranger, which is owned by Energy Resources of Australia, a subsidiary of Rio Tinto, has had more than 150 leaks, spills and licence breaches since it opened in 1981.

The Mirarr are also refusing to allow development of the nearby Jabiluka mine which contains one of the world's largest known uranium reserves.