The outsourcing company Serco apologized after accidentally sharing the email addresses of nearly 300 contact tracers.
The company is training staff to track Covid-19 cases for the UK government.
He made the mistake when he emailed new trainees to inform them about the training.
Serco said he apologized and reviewed his trials “to make sure this doesn’t happen again”.
The contact trace is a system used to slow the spread of infectious diseases such as coronavirus. It is already used in other countries including Singapore and Germany.
In the UK, health secretary Matt Hancock said 21,000 contact detectors have been hired, some of whom are health professionals.
They will collect contacts from Covid-19 patients and track those people by phone or email to slow the spread of the disease in the community.
Serco is one of the companies that hire, train and manage 15,000 contact detectors who do not have clinical training.
But the mistake may leave the company in violation of data protection regulations. It is understood that at least one staff member has raised the issue with the Information Commissioner.
The error did not involve patient data, but it will not be useful for a contact tracking project that is intended to ask many thousands of people who have fallen ill to share the details of their friends and acquaintances.
Serco wrote the email to tell new trainees not to contact the help desk in search of training details.
But the staff member who sent it enters their email addresses in the CC section of the email, rather than in the blind CC section, revealing them to all recipients.
When the Ministry of the Interior made a similar mistake last year, he referred to the Information Commissioner, but Serco has no intention of doing so.
A Serco spokesperson told the Today program: “An email has been sent to new recruits who have given us permission to use their personal email addresses.
“By mistake, the email addresses were visible to other recipients. We apologized and reviewed our processes to make sure this didn’t happen again.”