THE World Heritage-listed Kakadu National Park will be expanded to include thousands of hectares of ecologically sensitive land that has uranium worth billions of dollars.

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

Mr Lee, the 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.

Mr Lee is an extremely shy and humble man who shuns publicity. "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," he told The Age in a rare interview in 2007.

The Age has now learnt that the Northern Land Council, an organisation that represents Aboriginal groups in northern Australia, has written to federal Environment Minister Peter Garrett offering the land on behalf of Mr Lee.

For years, the pro-mining land council delayed relaying the offer to the government as Areva held out hopes of extracting the uranium on 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.''

The Koongarra deposit is three kilometres from Nourlangie Rock, one of Kakadu's most visited attractions.

According to Aboriginal beliefs, the land includes places where the rainbow serpent entered the ground, and is home to a giant blue-tongue lizard that should not be disturbed. It is also said to include art painted on rocks hundreds, perhaps thousands or even tens of thousands of years ago.

Before moving to incorporate Koongarra into Kakadu, the federal government must go through a legal process, including seeking a response from Areva. But Mr Garrett said the opportunity to include the land as part of Kakadu was ''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 Age.

The blocking of the mine comes five years after the federal government under John Howard took control of uranium mining from the Northern Territory Labor government - a move designed to boost production at a time of soaring prices for the ore.

Instead, in the face of ongoing concerns of traditional owners about the impact of mining on their land and ancient culture, companies such as Areva continue to struggle in their efforts to extract tens of billions of dollars worth of northern Australia's known uranium deposits.

The Mirarr traditional owners are opposing a massive expansion of the controversial Ranger uranium mine, which is surrounded by the Kakadu park, because of concerns about inadequate environmental protection. The Age revealed this week that millions of litres of radioactive water have flowed from the mine into Kakadu in a series of environmental mishaps since December.

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 the development of the nearby Jabiluka mine, also owned by ERA, which contains one of the world's largest known uranium reserves.

The Australian Conservation Foundation - a critic of uranium mining - said the federal government should 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 time,'' the foundation's nuclear campaigner, Dave Sweeney, said.