Campaigners are furious that council planners' recommendation on the King Alfred project could be made before public consultation ends.
Their initial report on whether the controversial scheme should go ahead will be discussed by Brighton and Hove City Council's planning committee on March 23.
By then the councillors will have had five days to study the planners' report into the application.
However, the public consultation does not end until March 21. Documents received after March 19 will not be included in the initial report and not taken into account when the planning officials make their recommendation to councillors.
A new sports complex, shops and 751 homes are planned for the site of the crumbling leisure centre, which has been the subject of a series of failed development bids.
Valerie Paynter, of the Save Hove campaign, who opposes the £290 million project, said the decision to hold the meeting on March 23 was an affront to democracy.
She said: "Given that the report for such a meeting would have to be written and available for public inspection a full week before any such meeting takes place, I am unable to see how it can be legally or ethically appropriate to hold a committee meeting to determine the application on March 23."
She said the needs of canvassing councillors, who will be door-stepping residents in the run-up to local elections on May 3, should not be put before the proper democratic process.
Council officers have defended the decision, claiming that holding the meeting two days after the end of the consultation was legal and not uncommon.
City planner Martin Randall said: "The report will be written on the basis of all information known at the time it is printed and will clearly refer to the fact that it has been written on that basis.
"All representations received after the report has gone to print will be referred to in an addendum report to be circulated and referred to at the meeting."
He added that the inhouse legal team had ruled the decision was "lawful".
He said: "Careful consideration has been given to the setting of the committee date, regard being had to the sensitivities of this particular application and the nearness of the local elections.
"On this basis there is no intention on the part of the local planning authority to move the committee date back." The council refused to elaborate on why the meeting could not have been held later.
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