Opponents of Donald Trump's proposed £1bn golf resort in Aberdeenshire claim they have thwarted his plans to forcibly purchase land in a mass protest backed by celebrities and conservationists.

Scores of people including comedian Mark Thomas and mountaineer Cameron McNeish have been made joint owners of one acre of land previously owned by Michael Forbes, the quarryman and salmon netsman who has become Trump's most famous opponent.

The land is part of Forbes's 23-acre property which sits inside the proposed resort close to one of two planned 18-hole golf courses and, in a play on words, has been nicknamed The Bunker.

Campaigners in the protest group Tripping up Trump today unveiled an online appeal for sympathisers to register their names as joint owners, in a campaign likened to the mass purchase of land next to Heathrow to block the airport's third runway.

Although Trump has said Forbes's home is not necessary for his resort, the billionaire property developer's executives have said he could seek the compulsory purchase of Forbes's land and three other private houses and properties inside or next to the site.

Trump, who flew into Aberdeen today with his son Donald Trump Junior, already has outline planning permission for these properties. His latest masterplan included all five parcels of private property in the resort.

Two property owners, a driving school instructor who lives next to Forbes and Aberdeenshire council, have indicated they want to sell to Trump; Forbes and David Milne, another prominent objector who owns an adjacent former coastguard station, are resisting the measure.

His opponents are convinced Trump will seek their compulsory purchase order and believe their mass ownership of part of the land will make it legally and politically difficult for Aberdeenshire council to agree to the order.

Forbes, made famous after Trump singled him out for abuse in 2009, said: "Tripping Up Trump now own a piece of my land in an effort to help protect my family and the other families worried by the threat of compulsory purchase. Trump lost the battle for public opinion long ago, and he's now lost any chance of bulldozing our homes."

The group's solicitor, Eileen Bready, added: "The Tripping up Trump campaign has now acquired land at Mill of Menie to defend the homes under threat of compulsory purchase. The Trump Organisation will now have to deal with many more objectors than they anticipated."

Other co-owners of the one acre site include Dr Adam Watson, the ecologist and expert on the Cairngorms; Paul Young, the actor and presenter; Ed Wardle, the adventurer who recently made a survival series in the Canadian wilderness; Scottish Green party MSP Robin Harper; other residents threatened by compulsory purchase; and Tripping up Trump activists.

In a statement, Watson said: "I've decided to help prevent Aberdeenshire folk from the harassment and threat of removal from their homes, merely to satisfy a private developer who asserts he now wants the land."

Thomas said: "If Aberdeenshire council does the bidding of a US billionaire to turf people off their land they are nothing but lackeys and clerks for the golfing clearances."

Trump has said he wants to create "the world's greatest golf course" on the stretch of coastline, part of which is a legally-protected conservation area of rare and valuable sand dunes.