Central Science Laboratory (CSL), a UK government executive agency, criticised the campaigns group study that found 57 PepsiCo and Coca-Cola drinks in India containing between three and five different pesticides.
CSL, which has tested drinks for Coca-Cola, said in a letter seen by BeverageDaily.com: "There is no evidence in the report that, even if the pesticides were present, the levels were measured with any accuracy".
It added that "as written, the report does not provide unequivocal confirmation of identity of the pesticide residues claimed to be found".
The letter bolsters the position of Pepsi and Coke, which have tried to counter fierce public criticism of their drinks by politicians and almost all media organisations in India since the release of the pesticide study last week.
Average pesticide levels in drinks were 24 times above the Indian government's proposed maximum, according to the study, which was published by Centre for Science and Environment (CSE).
Several Indian states have since banned soft drinks from public buildings.
One of the most vocal has been Kerala, which on Wednesday said it would ban both the production and sale of Coca-Cola and Pepsi drinks across the state."We have arrived at the decision to ask both Coke and Pepsi to stop production and distribution of all their products, based on scientific studies which have proved that they are harmful," said Kerala chief minister Velikkakathu Achuthanandan.
The bans threaten to damage PepsiCo and Coca-Cola's sales in a soft drinks market growing at between seven and eight per cent per year.
It is the second time in three years that the CSE has released data showing Coke and Pepsi drinks contaminated with pesticides in India.
Both Pepsi and Coke again tried to reassure consumers this week. PepsiCo told BeverageDaily.com: "For three years we've looked very hard at this and engaged some of the best scientific minds in the world, and all the data and all the science consistently point to the fact that our products are absolutely safe."
Coca-Cola said it had been testing drinks regularly at the UK's CSL lab and no pesticides had been detected. The two drinks companies said they complied with international standards.
CSE said its Indian lab had the international quality standard ISO 9001:2000, and that it used state-of-the-art GC-MS testing equipment.
The Indian government was reportedly conducting its own tests this week in order to confirm the CSE findings.
India's Supreme Court, meanwhile, has demanded to see a complete ingredients list for the affected Coca-Cola and PepsiCo drinks. The move could force Coke to reveal its legendary secret ingredient, although the company is likely to fight hard to avoid that.
CSE's first study revealing pesticides in soft drinks, published in 2003, was eventually endorsed by India's Parliament, despite soft drinks industry criticism of the testing.
As a result, standards for pesticide levels in fizzy soft drinks were drawn up the by the Bureau of Indian Standards, but continued debate and lobbying has kept them from being implemented.
The provisional limits are 0.1 parts per billion (ppb) for individual pesticides in fizzy drinks and 0.5ppb for total pesticide content. CSE's latest test results, spread across 11 brands, found more than 11ppb of pesticides in soft drinks on average.
Some scientists have pointed out that a range of foods in India contain pesticides, and that the problem is not specifically with soft drinks but with controls on pesticide use in the food chain generally.