Uranium aspirant Toro Energy has been dealt a blow on the eve of the Christmas break, with Environment Minister Tony Burke refusing to approve the company's plans for Australia's next uranium mine at Wiluna.

While Mr Burke has not rejected the proposal, he has not approved it today as many in the market had expected.

Instead he has told Toro that more information on certain matters is required before the mine - located in Western Australia's harsh interior - can proceed.

Mr Burke has extended the deadline for a decision to be made to March 31, 2013, but has also indicated he may give his ruling earlier than that.

Toro chief executive Greg Hall told BusinessDay this afternoon that it was not yet clear what extra information was being sought by Mr Burke.

''We need to clarify that ... once we find that out we will know for sure,'' he said. ''Toro is very surprised and extremely disappointed with this further delay.''

While the market may not have expected a delay to approvals for the Wiluna mine, environment groups had been confidently predicting for some time that Toro had not done enough to satisfy the approval conditions.

A recent consultant's report commissioned by the Conservation Council of Western Australia predicted that certain measures around storage of tailings were not adequate to meet federal approval.

Council spokeswoman Mia Pepper said Mr Burke's decision was prudent and responsible.

''The Toro project is ill-conceived,'' she said.

Australian Conservation Foundation spokesman Dave Sweeney said Toro was a small company that would struggle to raise the funds needed to get the Wiluna project off the ground.

Toro will have a change of leadership in February when Mr Hall steps down and is replaced by Dr Vanessa Guthrie.

That transition has already made headlines for making Toro what is believed to be the only ASX company with an-all female leadership, given that its chairman is Erica Smyth.