Green councillors will boycott the crucial meeting to decide whether Brighton and Hove Albion can have a stadium at Falmer.
They say the city council has already decided in principle not to stand in the way of the application for a site at Village Way North.
Councillor Rik Child said there were gaps in the information being given to members of the planning committee for their meeting at Hove Town Hall tomorrow.
He said: "The information on which the committee is being asked to make its decision is incomplete and contradictory.
"Quite apart from not thinking Falmer is the best location for a stadium, we believe the application will be rejected at a public inquiry leaving fans and the club high and dry, with only the council to blame for its lack of leadership."
Coun Child said a transport interchange and coach park would be in downland and could be in the new national park. The scheme would also overload existing roads.
There would be a severe impact on Stanmer Park and there had been objections from many organisations, including English Nature and the Countryside Agency.
Coun Child said: "The very effective Falmer for All campaign and the Labour-run council have built a rollercoaster of support which is difficult for anyone to resist.
"But might is not always right. Those people who have opposed the Falmer bid have been branded as being anti-football and anti-Albion and this is just not true.
"We believe it's important to speak out for what we believe and right now we're crying foul."
Councillor Bob Carden, the Labour councillor who will chair the meeting, said: "It will be down to the committee. I don't know which way people will vote.
"I have tried to be fair and have extended the time for people to speak to half an hour for each side.
"All issues before the planning committee have a recommendation from officers and in this case it is in favour.
"But the planning committee has to decide matters on planning issues and we will have to be satisfied one way or the other before making a decision.
"We are lay people and we will be the ones making the decision on the day."
Paul Samrah, from the Falmer for All campaign, said members had worked extremely hard to try to get a result.
He said: "We are hoping for the right decision but we are taking nothing for granted.
"Wednesday is a milestone. An application for a community stadium has gone before the committee and we hope the councillors will approve it."
Labour councillor Pat Hawkes has written to the council to support the application. She cannot attend the meeting as she will be representing the council at a conference.
She said most people in Stanmer ward, which she represents, had indicated their support and she said: "I believe it will be a beneficial development here in north Brighton."
Coun Hawkes, who chairs the children's committee, said the community stadium would help the sporting and educational needs of many youngsters.
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