Proctor, who has been with City since the start of the season, will play his final game for the Bantams in Saturday's First Division match with Norwich before returning to Sunderland.
Bradford manager Nicky Law said: "I spoke with Howard Wilkinson on Friday morning and he said that he wanted the lad to go back to Sunderland so that they could have a look at him and assess whether he is ready for the first-team.
"It is a major blow for us because I liked the lad and felt he was doing a good job for us.
"It meant a lot of time on Friday phoning around and trying to bring in a replacement, but that was not easy and I will need to keep on working hard on that over the weekend and again next week.
"Hopefully we can bring in one, maybe two loan signings, I have the targets in mind but we will have to be careful because of the financial restraints we are under. I cannot go to the big clubs and ask to loan out players who are earning thousands of pounds a week."
NORWICH MATCH PREVIEW