Campaigners say 21% of people at workshops did not disclose on their applications relationships with firms being discussed

More than one in five attenders at EU events on regulating big tech companies did not disclose links to the industry when applying to take part, according to transparency campaigners who say hidden networks are distorting public debate.

Researchers at three NGOs analysed nearly 4,000 registrations at European Commission workshops organised earlier this year to test companies’ compliance with the Digital Markets Act (DMA), a law to curb anti-competitive behaviour.