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Last weekend's Washington Post featured a front-page article about the mounting allegations of scientific censorship at the USDA, often to appease politically powerful agricultural companies like Monsanto.

You heard that right: when independent, government scientists produce research that threatens corporate agribusinesses, the USDA—according to at least 10 government scientists—censors the results, waters down the findings and punishes the researchers.

• It's time for the USDA and EPA to come clean over RoundUp residues

Consumers groups have been calling on the US government to test foods for glyphosate residues on behalf of the public, to try to determine what levels may be found and if those levels are dangerous. But so far those requests have fallen on deaf ears.

It would seem that would be an easy request to meet. After all, since 1991, the US Department of Agriculture has conducted a 'Pesticide Data Program' (PDP) that annually collects pesticide residue data for hundreds of pesticides.

The testing looks for residues on a range of food products, including infant formula and other baby foods, and also looks for residues in drinking water. The purpose of the program is to "assure consumers that the food they feed their families is safe", according to the USDA.

But while the USDA looks for residues of other herbicides, as well as fungicides and insecticides, the agency routinely does not test for glyphosate. It did one 'special project' in 2011, testing 300 soybean samples for glyphosate, and found that 271 of the samples had residues. The agency said all fell within the range deemed safe by the EPA, and has since said that testing for glyphosate is "not a high priority."

In the latest annual PDP report - issued yesterday, 11th January - once again, glyphosate data is absent. Testing was done to look for residues of more than 400 different herbicides, insecticides and other pesticides on food products. But no tests reported for glyphosate.

The USDA says it is too expensive to test for glyphosate residues; much costlier than tests for the other 400+ pesticides that are part of the analysis, the agency says. The agency also echoes the position held by Monsanto that glyphosate is safe enough that trace amounts in food are nothing to worry about.