The building of a new Everton stadium could create up to 1,250 permanent jobs and 1,000 homes, a report has claimed.
The study, commissioned by Liverpool City Council, said the move from Goodison Park could take up to 50% of the 130-acre Walton Hall Park.
Liverpool Mayor Joe Anderson said the report is an independent investigation into the potential impact and "in no way a plan or an agreement".
Campaigners said the report ignored the "major" issue of traffic and parking.
A spokesperson for the Save Walton Hall Park group said "not a lot of the park will be left to improve" if 40 to 50% was lost to the stadium development.
Everton has been in talks with Liverpool City Council to collaborate on a new stadium since June 2013.
Mayor Anderson said: "I can state that, at this time, no plans have been presented to us by Everton FC, but clearly it would be irresponsible of us to allow anyone to come to us with any proposal, for anywhere in the city, without us first taking a full and in-depth look at the situation."
The feasibility study, conducted by consultancy firm Volterra Partners, said the proposed stadium could accommodate 50,000 fans and remaining green space "would be upgraded".
It reported 30,000 sq m (323,000 sq ft) of leisure and retail space could be created if Everton moved to the park, originally opened to the public in 1934.
The scheme could also include university facilities for sports, a school and a bigger health practice.
The study added current facilities could also be provided as part of the redevelopment, including the leisure centre, children's play area and sports pitches.
A Save Walton Hall Park spokesperson said
"We will have a generation of children who will never live and play in local parks and green space. They will live in a concrete jungle.
"The report looks good on paper [but] in the real community they do not always work."
The 41,000-capacity Goodison Park is one of the oldest football stadiums and has been the home of Everton since it opened in 1892.
Their local rivals Liverpool revealed plans in April to increase their stadium's capacity at Anfield from 45,500 to almost 59,000.