Oil giant Shell's application for a licence to explore for gas in the Karoo should be put on hold, the DA said.

The party warned of the risk of the prospecting contaminating water.

"The proposal by Shell to explore for gas over 90000km² of the southwestern Karoo Basin is premature and should not be entertained by the Petroleum Agency of SA," DA water and environmental affairs spokesman Gareth Morgan said.

The DA was concerned about the use of hydraulic fracturing ("fracking") in the prospecting because it consumed immense quantities of water and had the potential to pollute aquifers.

"The process is highly controversial and has been banned in several areas in the US," said Morgan. "The precautionary principle has to apply when considering any proposal that involves hydraulic fracturing.

"For the moment, we simply do not know enough about the deep geology of the Karoo, nor is it evident how the already water-stressed Karoo could provide the water for this thirsty activity."

"The DA believes that there should be a moratorium on [this]."

Shell's Phaldie Kalam said the group was identifying concerns, and assessments of the effects of the explorations on the soil, surface water and groundwater, and of social considerations, would be made.