The inquiry into the proposed £50m Rushden Lakes retail and leisure park, which starts in six weeks, has been extended to cope with demand.
Due to the level of interest and the number of people who are expected to give evidence at the hearing, the planning inspector has extended the length of the inquiry from eight days to 12.
So far, 886 responses to the plans have been received from interested parties.
A spokesman for East Northamptonshire Council, which will host the inquiry at its Thrapston offices, said: “The planning inspector will hear from all interested parties and their legal teams.
“At designated times, members of the public, local businesses and neighbouring councils will be given the opportunity to speak.
“The council is expecting the chamber will be at capacity during the initial days of the inquiry.
“Further updates will be given nearer the time as details are confirmed.”
East Northamptonshire Council approved planning permission last year, but following opposition from Corby, Kettering and Northampton councils the decision was called in by Local Government Secretary Eric Pickles, who decided a public inquiry should take place.
The plans are backed by the town councils in Rushden, Higham Ferrers and Irthlingborough, and by Wellingborough Council.
Irthlingborough Town Council leader John Farrah said: “Irthlingborough Town Council is backing it. We had a stall at the Rushden Cavalcade recently and 90 per cent of the people we spoke to wanted it. We will be at the inquiry and we will have a speaker.”