SHANE MCLEOD: Environmentalists and traditional owners are complaining that Energy Resources Australia has failed to properly report a potential contamination leak in the heritage-listed Kakadu National Park. They claim it demonstrates a lack of transparency by the Rio Tinto-owned company.

For its part ERA denies a spike in electrical conductivity represents any breach in the mine's operating conditions. It says the mine remains one of the most highly regulated and scrutinised in the world.

Liv Casben reports.

LIV CASBEN: The Environment Centre of the Northern Territory says a significant leak of sulphate detected outside the uranium lease in Kakadu last month is evidence of ongoing problems with the Ranger mine.

Dr Stuart Blanch says the information was leaked to his centre. 

STUART BLANCH: The supervising scientist did not report this information on its website, it did provide it to a committee of interested folks, but this sort of information should be on its website. 

The information that it does have there completely masks and excludes the peak that shows that two times the reporting level of salt escaped from Ranger on around the 10th of April this year, but they did not report it. 

LIV CASBEN: ERA says it is possible that these leaks have come from the Ranger operations but equally that it's possible that it's come from somewhere else. Just how sure are you that it has come from Ranger?

STUART BLANCH: Look I think Ranger should be honest and say it's probably from our site we don't know what happened, but we're going to fix it up. They should have been on the phone to the Aboriginal community who are surrounding and living around this site and who are watching the operations. They should have been on the phone to us and they should have made sure it was reported. 

If they don't think it's a problem then they should be honest and open about it rather than waiting for people to leak it to us.

LIV CASBEN: Justin O'Brien from the Gundjeihmi Corporation says it damages the historically good relations traditional owners have had with the mining company.

JUSTIN O'BRIEN: We've seen this data, we know this took place, they know this took place, they can't explain how it took place and the whole scenario is just patently inadequate

LIV CASBEN: But David Patterson from ERA says that while there has been a spike it doesn't pose any significant environmental risk.

DAVID PATTERSON: Well, there is, we've observed, in the normal monitoring of water quality in the creek, that there has been a spike in electrical conductivity, it remains within the operating criteria for the mine. So there has been no breach of our operating conditions and we're investigating the source of that spike.

LIV CASBEN: So is ERA responsible for this spike, or could've it have come from somewhere else?

DAVID PATTERSON: It's possible it could've come from somewhere else, it's possible it could have come from on our lease, and we're investigating that.

LIV CASBEN: Environmentalists say if salt is released then uranium could have been released as well. What do you say to that claim?

DAVID PATTERSON: Well the uranium levels are being monitored and are published and are publicly available and are available from the office of the supervising scientist and they don't confirm that hypothesis.

SHANE MCLEOD: David Patterson from Energy Resources Australia ending that report by Liv Casben.