The federal government has warned the state of Oregon off imposing strict labelling on genetically modified foods, saying it could make it difficult for food producers to market their products nationwide.

Oregon citizens are to vote on Measure 27 on 5 November. If passed, the measure would make Oregon the first US state to require all genetically modified foods sold in the state to alert consumers to the fact on packaging.

A letter from Lester Crawford, deputy commissioner of the Food and Drug Administration, was sent to the office of Oregon governor John Kitzhaber, reported USA Today. The strongly worded letter claimed the measure “would impermissibly interfere with manufacturers’ ability to market their products on a nationwide basis”.

The EU and Japan already require products with GM ingredients to be labelled as such. In fact, the EU is currently tightening up its labelling legislation with the effect that, from 17 October, any foods with more than 1% GM content must carry GM labelling. If Measure 27 were passed, Oregon would become the first state to require labelling of GM foods.

Many producers are wary of the measure, as they will then have to provide special labels for foods to be sold in Oregon. If the measure is passed, it is likely to open the floodgates for similar actions in other states.

“In this letter, we are not promising to take action, but we are letting the people of Oregon know, as best we can, what our views are about the ordinance,” the report quotes a senior FDA official as saying.