The inquiry was then shown an email chain involving several consultants which Mr Harvey was copied in to.
In an email on 29 June 2016, Dr Murthy Saladi said: "At the moment we are all under suspicion and the only agency who can investigate all of us I believe is the police."
Another consultant, Dr Ravi Jayaram, replied to say that he and Dr Stephen Brearey were "trying to meet with the execs ASAP to discuss exactly this" but "they do not seem to see the same degree of urgency as we do".
Mr Harvey then replied to all the doctors on the email chain to say "this is absolutely being treated with the same degree of urgency… all emails cease forthwith".
Asked why he asked all emails to stop, he said he was trying to "dampen down" an "extreme situation".
"I fully accept that I got that completely wrong," he said.
"That email doesn’t read as it should have done.”
Earlier, as he began giving evidence, Mr Harvey asked to address the inquiry and said he was "sorry for the hurt" that had been caused to the families of Letby's victims.
"It was only ever my desire to have a safe hospital and to be able to tell the parents what had happened on the neonatal unit, and if I failed in those aims, I am truly sorry," he added.
Letby is serving 15 whole life terms in prison after being convicted of seven counts of murder and eight of attempted murder, including two attempts on the same victim.
The inquiry is due to sit until early 2025.