Portobello Park Action Group [PPAG], which is fighting to save a disputed piece of green space, plan to convince MSPs to back their cause at a meeting today.
The campaigners say plans by City of Edinburgh Council to build its long-overdue Portobello High School on the parkland would set a precedent for all councils to build on "common good" land, even if local residents oppose it.
They have called for the school to be built on an alternative site.
The row over the school has gone one for years and previously resulted in a ruling at the Court of Session in Edinburgh in favour of the park's supporters.
But in January, MSPs unanimously supported a Bill paving the way for the school's construction.
Former Edinburgh councillor and PPAG represenative Stephen Hawkins said: "If the Portobello Park Bill goes through, not only will it enable the City of Edinburgh Council to override its citizens' right to common good land in Portobello, it could set a principle for other councils across Scotland to ride roughshod over their residents' common good land too.
"PPAG fully supports the urgent need for a new Portobello High School on one of the several available sites but believes that the council has misrepresented the facts, thereby pushing it through council processes and dishonestly boosting public opinion in favour of building the school on Portobello Park.
"There are reasonable alternative sites, but the council seems disinterested [sic] in them. We have also been promised that if the new building is put up in Portobello Park, the existing school site will be turned into green space."