The EU's foreign policy chief Josep Borrell is under fire over allegations a report was watered down following Chinese pressure.
Questions hang over the revisions to a text on disinformation about COVID-19.
It comes after the New York Times reported EU officials delayed and changed parts of the document.
"I absolutely refute and dispute any claims that in our reporting we are bowing to any kind of external pressure," said Peter Stano, a spokesman for the European Commission.
"The notion of having this report published on Friday after water it down, after changing it, is just misperception of the processes which go in any institution including the media where I guess you have internal communication that is for internal use and then you have something else focused on your public output."
The report was published on a site established by the European External Action Service — the EU's foreign affairs ministry led by Borrell — to highlight disinformation campaigns.
The text notes “there is evidence of a coordinated push by official Chinese sources to deflect any blame for the outbreak of the pandemic".
But the New York Times claims in a previous version of the text, sentences were removed and language toned down.
Now a Dutch MEP is sending a letter to Borrell for an explanation.
"I want to be very nuanced, there is no real proof of any will to misinform, I'm just asking Mr Borrell to give an explanation," said Bart Groothuis.
"Have I seen other instances? Well, if you look at the German newspaper Die Welt, they wrote a story today that the German government said 'Well we're being pressured by [the] Chinese once in a while and it's very annoying'.
"And I think the Chinese are getting bigger, stronger, their economy is growing really fast, at least before corona, but it will pick up, and they will be trying it again.
"It's a moment in time when we should say as Europeans we're sovereign we don't accept it, don't try it again."
China's foreign ministry has vigorously denied it was spreading disinformation, saying it was a victim, rather than a sponsor of false reports.