The Guardian said it was concerned that the producers did not have a good experience.
It said their allegations were discussed during a mediation process and were only a partial version of events.
It added that the slavery podcast will pull no punches in addressing The Guardians history.
The GuardianGetty
Deadline knows the identity of the person who sent the email, but has chosen not to name him.
The two other individuals who signed the email were engaged as freelancers on The Guardian project.
They claimed that this was ignored for weeks and minimised before they were offered ineffective mediation sessions.
The outcome of this project is a huge indictment of the paper.
The project is largely complete and will not pull any punches in terms of transparency.
The podcast is now close to completion.
Taylor, the son of a cotton merchant, founded The Manchester Guardian in 1821.
The producer who sent the email has not repsonded to repeated requests for comment.
We made numerous attempts to have good-faith conversations with our team to no avail.
The institution is now looking for other producers to finish our work and has ignored our concerns.
The outcome of this project is a huge indictment of the paper.
