The Priory Park Preservation Society hopes they will all attend the discussions at the Civic Centre.
Society chairman Peter Walker said: "This will be the first opportunity for members of the public to speak to councillors since the preferred option was published in the Civic News."
He meeting takes place the day before the council's cabinet meets to make its decision on whether to go ahead with the scheme.
Mr Walker added: "We expect a big turnout of members and the public.
"We want to make absolutely certain councillors are fully aware of the strength of feeling against the damage which would be done."
Councillors invited are Ron Price, Anna Waite and Murray Foster from Prittlewell Ward, Brian Houssart, Simon Gorham and Mike Dolby from St Laurence Ward, and the three leaders, Tory Charles Latham, Labour's Chris Dandridge and Liberal Democrat Graham Longley.