The failure of England's public healthy body to publish results of three major studies into vaccines for children makes it impossible for experts to establish whether the drugs could be harmful, scientists have claimed.

Hundreds of children took part in three potentially risky Government drug trials, but Public Health England (PHE) breached the law by failing to add the findings to the official register set up to allow the scientific community to scrutinise the outcomes.

Experts have accused PHE of an “incomprehensible” violation of the trust of parents who gave their consent for their children to take part in the tests.

The largest trial involved 640 participants under the age of 16 whose parents gave consent for them to be selected at random to try a new meningococcal and whooping cough booster vaccine.

While dangerous side-effects in a trial at this stage are rare, a risk does exist. Participants also take a gamble by offering themselves up for selection for a new drug which might not protect them as well as the standard therapy.

The trial concluded in 2016, but the results have not yet appeared on the EU Clinical Trials Register (EUCTR), in breach of EU law which requires registration within 12 months, nor published anywhere else.