The complaint was brought against the petroleum company's adverts that appeared in the Sunday Times and other newspapers by theTreasure the Karoo Action Group, which has been campaigning against the use of the controversial technique to extract shale oil in the Karoo.
The ASA dismissed four of the nine complaints, upheld four and did not make a decision on one complaint as it fell outside its mandate. However, the ASA said that in its opinion "the claim and reference does not fall foul of the provisions of the (advertising) code".
Shell SA said it was reviewing the grounds of the ruling.
"We are disappointed by the ruling. The purpose of the advert was to provide information direct to the public to enable them to properly assess the nature of the proposed shale gas exploration in the Karoo, as well as the accompanying technology of hydraulic fracturing," said Shell SA chairperson Bonang Mohale.
He said the advert was a technical statement of the company's opinions and understanding of the implications of shale gas exploration in SA.
"The advert was intended to bring to the public's attention, in an open and transparent manner, Shell's commitments and information that are already in the public domain," he said.
In its reply to the ASA, Shell refuted allegations made by the Treasure the Karoo Action Group that the advert was "misleading, dishonest, untruthful and prepared without any appropriate sense of responsibility".
Mohale said: "We consider the advert, along with our environmental management plan, which has been available since March, as part of our duty to keep the public informed of our proposed exploration project. The subject is technically complex, spanning the fields of science and engineering and we believe it is in the interest of the public to hear our views."
Mohale said that natural gas could bring jobs and electricity to many South Africans while helping to reduce CO2 emissions. "It needs to be done responsibly and we welcome the public debate."
The government imposed a moratorium on shale gas exploration in the Karoo earlier this year on concerns that there was not enough information about the long-term effects of fracturing, through which water and chemicals are pumped into the ground through a drill rig to force the gas to flow.
Treasure the Karoo Action Group has welcomed the ASA's ruling.
Last month France became the first country to ban the technique outright.