Campaigners claim plans for a sports centre of excellence in Gloucester Park are being "railroaded" and have demanded a public meeting.
Residents Against Park Exploitation (RAPE) want to meet with councillors to air concerns.
The action group, who battled against Billericay Town Football Club moving to the park until the plan was shelved, are unhappy with Basildon Council three multi-million consultation options for the centre.
RAPE campaign planner Dave Wurakon said: "We are not averse to improving sports facilities in Basildon but are unable to support the proposed centre at this time. We believe that residents must be made aware of all the facts in order for them to make an informed decision."
The major development could include an Olympic-size swimming pool, gymnasium, health centres, sports halls and dance studios near the existing athletics track.
Tory cabinet member for leisure councillor Tony Hedley, who is spearheading the project, insisted: "We are carrying out one of the most wide-ranging consultations into this and anyone is welcome to come and discuss it at meetings held across the district.
"We are adding a fourth option for those who do not want it, but I believe they will be far outweighed by those who do.
"RAPE asked for a meeting with our consultants PMP, where I could have discussed it with them, but refused to allow me to attend.
"More than 100 school children came to a display about it in the Towngate Theatre and were very enthusiastic.
"It is sad that there is such negativity about what is a positive move to improve the district's sport."
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