The Friends of Lion Farm Playing Fields group formed a human chain at the fields in Oldbury to highlight their opposition to plans they claim have been brokered in secret.
Protestors are against proposals for a designer outlet shopping centre on the council-owned land that developers says could create 2,000 jobs and attract £200 million of investment to Sandwell.
Pete Durnell, acting chair of the campaign, said the numbers of local people protesting on Wednesday evening showed the strength of feeling against the proposal.
“Theses fields are very much valued in the community," he said.
"The vast majority are saying that this development is ridiculous given that there are major stores, like M&S, closing down around the country.
“So there is a lot of concern that this site could be built on but the shops will never been taken up and stand empty but mostly people just want to protect their local green spaces.”
Campaigners claim decisions around the proposed development have been made behind closed doors; a claim dismissed by Sandwell Council which says the proposal by developer Jeremy Knight-Adams has been widely reported in the press and published in public council papers.
The company has also stated that their final plans for the shopping centre on the site close to Junction 2 of the M5 will be open to public scrutiny.
Protestors say they will now keep up the pressure in order to highlight their campaign ready for when a planning application is lodged in the autumn.
By Local Democracy Reporter George Makin.