Opponents of Donald Trump's proposed golf resort in Scotland claim they have thwarted his plans through the mass purchase of land, a device used by campaigners against the expansion of Heathrow airport.

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

The parcel of land is part of Forbes's 23-acre property in Aberdeenshire which sits deep inside the resort, close to the eighth and ninth holes of the first of two planned 18-hole golf courses. In a play on words, the protesters have dubbed their collectively owned site The Bunker.

Campaigners from the protest group Tripping up Trump also unveiled an online appeal for other sympathisers to register their names as joint owners.

Trump, who flew into Aberdeen today with his son Donald Trump Junior on his private airliner, already has outline planning permission for five parcels of private property within or on the resort's boundaries. All five properties are incorporated in Trump's masterplan for the resort.

The property developer tried to play down the significance of the mass-purchase campaign but said he plans to talk to Aberdeenshire council about pursuing the compulsory purchase of all five parcels of land. He insisted that would be the council's decision, not his.

He then reopened his long-running feud with Forbes and David Milne, another prominent objector who owns a former coastguard station on a headland overlooking the North Sea, describing their properties as "slums" and a "pigsty".

Claiming the total cost of the project had now fallen from £1bn to £750m, Trump said the campaign would have no impact on his plans for the first golf course. But it would affect the view from the five-star hotel, a point he plans to raise with planning officials.

"You cannot see Forbes from the golf course, but he does have an impact on the hotel," Trump said. "If we build a £300m or £400m hotel, I don't think you want the windows looking down on a slum. I don't think anyone wants to build where your view is obliterated by a slum."

Milne's property was "a visual slum. It's a very unattractive house," Trump added.

The billionaire, on a three-day visit to tour the site and plan his first golf course layout, added he had unilaterally decided to rename the legally designated dune system that is being used for the golf course. A conservation area known officially as the Foveran Links, a site of special scientific interest, would now be called "the Great Dunes of Scotland".

"I think it's a more appropriate name, it's a bigger name, a better name and I think it's a name people can understand and relate to in Scotland," he said. "So I feel the dunes should be named for Scotland, not for myself. If I was being arrogant I would name them the 'Donald J Trump Special Dunes'."

Two of the property owners, a driving school instructor who lives next to Forbes and Aberdeenshire council, have indicated they want to sell to Trump.

So far, the co-owners of the acre include Dr Adam Watson, the ecologist; Paul Young, the actor; Ed Wardle, the adventurer; Scottish Green party MSP Robin Harper; other residents threatened by compulsory purchase and activists.

They believe their mass ownership will create severe legal and political difficulties if Aberdeenshire tries to seek a compulsory purchase order. It is understood the campaigners plan to fight any order right through the courts, bogging it down for years.

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."

Milne replied to Trump's comments: "My home may not be the most attractive on the face of the planet, but my extensions were designed and built under the requirements of the local authority. It's a great pity that his own carbuncles that he intends on erecting are not in keeping with the area in any way, shape or form."