Brighton and Hove Albion expect an average gate of 12,500 in their first season at the proposed Falmer stadium.
Chief executive Martin Perry said there was "no reason" to believe attendances would not be significantly higher at the purpose-built ground than at their present Withdean home, which can hold only 6,960 fans.
Charlie Hopkins, representing Falmer and Rottingdean parish councils at the public inquiry into the proposed 22,000-seat stadium, claimed the figure was not realistic.
He told the second day of the hearing at Hove Town Hall that the last time Albion attracted an average gate of 12,500 was in the 1982/83 football season.
But Mr Perry said: "The facilities at the Goldstone ground were considerably inferior to the facilities we would have at Falmer."
Mr Perry, being cross examined during his second day giving evidence, said the Seagulls had a large following and a big catchment area.
The club was in the top ten in England and Wales based on the amount of traffic on its web site.
Mr Hopkins said attendance at stadiums built by other clubs had not matched expectations after the first season and many had not been a financial success.
But Mr Perry said: "There is no reason to suggest 12,500 is a figure we would stay at.
"Good facilities attract new supporters. I would anticipate at the very least we would reach a figure of 15,000 plus."
The new stadium would be partly funded through a mortgage-type arrangement, which would in part be based on projected gate receipts.
The club says it would not need extra development around the Village Way North site to help finance the £48 million project.
Mr Hopkins criticised a Sussex Enterprise forecast, included in the club's evidence, that the stadium would boost the Brighton and Hove economy by £24.4 million in five years.
He said the actual figure could be more than £10 million less and the link between job creation and new football grounds was tenuous.
The club, however, says the new stadium would have a significant benefit on the area's economy and create more than 600 jobs in depressed East Brighton.
Supporters and objectors will speak during the inquiry, scheduled to run until April 8.
The inspector's report and recommendations will be sent to the Government in the summer. A final decision is not expected until September or October.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article