Proposals for the legal traveller site on Gorsebrook Road were raised at a meeting of the Labour Group, which included members of the planning committee.
A presentation on the preferred site was given to members during the meeting last month and a vote taken on whether the plans should progress to consultation stage, according to those present.
Interactive map shows site of the land:
Wolverhampton Council is under pressure to get the plans passed in order to protect green spaces in the city and Labour Group leaders are facing questions about whether party politics could result in pressure being put on planning committee members, who will decide whether it goes ahead.
The proposals have been met by a huge backlash from residents.
A senior Labour source said planning committee members should have been barred from the meeting.
The source said: "If the planning committee were to approve this anyone with anything between their ears would challenge it and take it to court, because they have already discussed issues in a political meeting.
"It's not fair and it's not right. This has never happened before. The issues should not have been discussed.
"If I was the leader I would have said we need a travellers site, are we in favour of it or not but no specific site should have been mentioned."
Councillor Roger Lawrence, who sits on the planning committee and also represents the St Peter's ward where the travellers site is earmarked for, said the plans were not discussed in detail and insisted he made it clear from the outset he could not comment.
WATCH: Heated public meeting over traveller site plans
He said: "I gave a statement that as a member of the planning committee I was not going to say anything to pre-determine the position and I assume other councillors I would have taken the same lead.
"I made it absolutely clear right at the start there was going to be a planning application. As far as I'm concerned the planning committee will determine this on planning grounds."
Conservative Group leader Wendy Thompson, who is also a member of the planning committee, said it was "open to suspicion" whether pressure was being put on Labour councillors to back the proposals but said she did not believe any rules would have been broken if planning committee members "sat at the back of the room" and were not directly involved in discussions.