A controversial application by oil giant Shell to explore for gas in an area of the Karoo should be put on hold, the Democratic Alliance said on Tuesday.
The opposition party warned that exploration would involve processes that risked contaminating surrounding bodies of water, but Shell countered that processes were in place to prevent this happening.
"The proposal by Shell to explore for gas over 90 000 km2 of the south-western Karoo Basin is wholly premature and should not be entertained by Petroleum Agency South Africa (PASA)," DA water and environmental affairs spokesman Gareth Morgan said in a statement.
The DA was particularly concerned about a process of hydraulic fracturing, also known as "fracking", which used immense amounts of water and had the potential to contaminate surrounding bodies of water with pollutants.
"The process is highly controversial and has been banned in several areas in the United States," said Morgan.
"The precautionary principle has to apply when considering any proposal that involves fracking, and 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," he said.
"The DA believes that there should be a moratorium on any exploration or mining activity that involves fracking."
Morgan said he had written to PASA CEO Mthozami Xiphu asking him not to consider Shell's application, or indeed any further applications, until a peer-reviewed study into the geology of the Karoo Basin, and an independent assessment of available water resources, had been undertaken.
Shell was currently compiling an environmental management plan.
"After this, PASA will consider whether to grant an exploration right for three years, which can be extended for up to six more years thereafter," Morgan said.
Shell's vice president for communications in Africa, Phaldie Kalam, said the company was in the process of engaging affected stakeholders in the area to identify concerns and would conduct specialist studies.
These would include soil surveys, surface water and groundwater surveys, noise, social and heritage impact assessments.
It said in order to avoid contamination of shallow aquifers, it would study rock formations before starting fracturing and make sure the fractures were contained in the boundaries of the targeted geological formation.
"In the Karoo, we expect that thousands of metres of rock separate the natural gas formations from the shallow groundwater aquifers. The risk of seeping gas in to aquifers or to the surface is extremely low."
Shell said it also used special barriers to contain fracturing fluid and prevent water contamination.