CONSERVATIONISTS say they may appeal a Government decision to allow Shell to drill near the World Heritage-listed Ningaloo Reef.

The Department of Environment said Shell could drill the Palta-1 exploration well, about 50km west of the Ningaloo Marine Park border, if it abided by conditions, including taking measures to avoid significant impacts on threatened species and migratory creatures such as whales.

The controversial decision has sparked outrage among conservationists, including The Wilderness Society, the World Wildlife Fund and the Greens.

The Wilderness Society WA marine co-ordinator Jill St John said the group would ask the Federal Environment Minister Tony Burke for a statement of reasons for his decision and for any evidence used to make his decision, before deciding whether to appeal to the Federal Court.

"In our view, this is an indefensible decision," Ms St John said.

"The Minister has failed to properly consider the location of this well in relation to the World Heritage Area, which is a Commonwealth protected matter.

Originally published as Greens in drilling Shell shock