The federal environment minister has approved the country's fourth uranium mine, to be built in South Australia's northeast.

Mr Garrett sang against the nuclear industry in his days as Midnight Oil frontman.

Now he's sure the new Four Mile mine ''poses no credible risk to the environment''.

Opposition environment spokesman Greg Hunt, who supports uranium mining, attacked Mr Garrett for his backflip on the issue.

''The promises Peter Garrett chose to make on uranium mining stand for nothing and nor does he, any longer,'' Mr Hunt said.

Mr Garrett said it had been a difficult decision to approve the mine but it was right for him to abide by Labor's policy, which allows for an expansion of uranium mining.

''The values that I had before entering parliament I hold dear,'' Mr Garrett said.

''[But] the Government has made a decision ... on this matter, which I fully accept.''

Prime Minister Kevin Rudd said the Labor Party had publicly changed its policy on uranium mining back in 2007, when the ''no-new-mines'' policy was dropped.

''It couldn't be more transparent than that,'' Mr Rudd told ABC Radio.

When asked why he didn't allow a domestic nuclear power industry, MrRudd said renewable energy and cleaner-coal technology was the best way for Australia to tackle climate change.

A nuclear-free campaigner with the Australian Conservation Foundation, David Noonan, said that the new mine's chemical and radioactive waste would leach into the groundwater.