The European Union’s foreign policy chief is facing questions over allegations that a report about Chinese disinformation over Covid-19 was watered down in response to pressure from Beijing.

In a letter to Josep Borrell, the Dutch MEP Bart Groothuis calls for a “formal and full explanation to the European parliament” about the evolution of an EU report on disinformation, amid emerging evidence it was altered under Chinese pressure.

The row escalated last week after the New York Times reported that EU officials had delayed and then rewritten the report after China tried to block its release. “The Chinese are already threatening with reactions if the report comes out,” Lutz Güllner, head of communications at the EU foreign service, wrote to colleagues last Tuesday, in an email seen by the paper.

The report was published on the EU’s monitoring website EU vs Disinfo on Friday. A survey of disinformation and misinformation about Covid-19 around the world, the report largely summarises and analyses publicly available information. It notes a “continued and coordinated push by some actors, including Chinese sources, to deflect any blame for the outbreak of the pandemic and highlighting bilateral assistance”, as well as “significant evidence of covert Chinese operations on social media”.

Groothuis told the Guardian that the EU appeared to have “caved in on substance”, as he said an earlier version of the report had provided details of false Chinese government claims. For instance, he said, it reported untrue claims from China that 80 French politicians had signed a statement using a racist slur to denigrate the head of the World Health Organization.

Groothuis, a former analyst at the Dutch ministry of defence, said it was extremely important for the EU’s senior management to back independent factual analysis. “China will become stronger, more prosperous and powerful, also militarily. It won’t be the last time they will try to intervene in internal politics of the EU.” He said it was time for the EU to send a clear signal: “If this is true, this can’t happen again in the future.”

Borrell, an outspoken former Spanish foreign minister, said last month that Europe needed to defend itself in the “global battle of narratives” over Covid-19, amid “a struggle for influence through spinning and the ‘politics of generosity’”.

The EU’s latest disinformation report, covering 2-22 April, is equally concerned by false claims and conspiracy theories from Kremlin-backed media. It states that “Russia and – to a lesser extent – China, have continued to widely target conspiracy narratives and disinformation both at public audiences in the EU and the wider neighbourhood”. Last month a leaked EU report concluded that pro-Kremlin media had been spreading disinformation with the aim of “aggravating” the public health crisis in the west.