Donald Trump stepped up the war of words with homeowners who live on the site of his golf resort development by describing one of the residents as stupid and branding his property as a slum.

The American billionaire, who flew to Scotland with his son Donald Jr to check on the construction work taking place at the Menie estate, near Balmedie in Aberdeenshire, singled out Michael Forbes, whose house is on land that would affect plans for a hotel on the site.

He was speaking after it emerged yesterday that pressure group Tripping Up Trump had bought a piece of land owned by Forbes in a bid to strengthen the voice of residents and prevent the council from using compulsory purchase orders to force the sale of the houses.

But Trump, who was met by a small group of protesters as he arrived at Aberdeen Airport, remained defiant about his plans, saying: “It is a little late to trip me up. It is a very sad situation that (Forbes’s) property is so poorly maintained. It is a pigsty. In the US we call it a slum.

“The hotel has a chance to be something outstanding. It is awfully hard when a window is overlooking a slum to say ‘let’s come to this beautiful hotel’. They will look out their window and see rusting oil cans.

“My mother was born in Stornoway. She was so meticulous. The Scottish people are very clean people and yet this guy runs the property like a slum. He lives in squalor.”

His comments brought a forceful response from Forbes, who disputed claims that he had twice agreed offers for his land but then rejected the deals. He said: “There’s no truth to this at all. He is a compulsive liar. The last time his son came here I chased him off the land.

“He’s got all these bodyguards with him and if he keeps saying these things about me then he will need them.”

Trump, 63, said it would ultimately be up to Aberdeenshire Council to decide whether to progress with a compulsory purchase order. He said he thought Forbes was stupid to have sold part of his land to protesters and said he might feel differently about wanting to buy the land if it was in a different state.

He added: “If he cleaned up his property I’d feel good about it. He should clean up his property for himself and for Aberdeen.”

He claimed that Forbes had twice agreed to sell his property before backing out of the deals. He said: “This is not a man who is so in love with his land he cannot see straight. Forbes made a deal with us twice and then broke the deal and then goes around saying what a bad person I am … story of my life.”

Environmentalists have criticised Trump’s plans amid fears that the new golf course will ruin the Menie dunes, a site of special scientific interest. The businessman yesterday announced that he was renaming them The Great Dunes of Scotland, in honour of his mother, Mary MacLeod, and the country.

“I feel that the dunes are so spectacular and so important that we should name them after Scotland,” he said. “It is a great name, a name that people can understand and relate to.”

Responding to claims from protesters that it was arrogant to rename the sand dunes, Trump said: “Arrogant would be if I called them the Donald J Trump special dunes.”

He originally unveiled his plans for a £1 billion golf resort in 2006, but said yesterday that it was now predicted to cost £750m because of the rising value of the dollar to the pound and cheaper building costs. He said he had already invested $60m (£41m) in the project and everything, apart from the hotel, was being financed by him.

“I don’t even have a mortgage on the site,” he said. “I don’t rely on banks. I don’t need banks.”

Trump has insisted the 18-hole course will be a championship one and will bring tourism with it, injecting millions of pounds into the local economy.

A family affair as American tycoon plays up his Scots heritage

He arrived with one mission in mind. “Okay, we’ll have some fun,” he told the assembled reporters, photographers and camera crews, before adding: “I hope my hair didn’t blow too hard out there.”

Minutes earlier the Trump private plane, painted black and red with gold lettering spelling out his name, had touched down at Aberdeen Airport for the businessman’s three-day visit to his development on the Menie estate. With his son Donald Jr by his side, and representatives from the Golf Channel following his every move, the Trump charm offensive began as he described his plans for the £750 million development.

“This will be a masterpiece,” he said. “When it is complete I think that everybody in Aberdeen and Scotland will say ‘thank you’.”

Trump, dressed in a smart black suit with bright red tie, spoke several times of his Stornoway-born mother, Mary MacLeod, at one point reminiscing about being told to clean up a piece of paper he had dropped on the floor as a child.

Keeping it in the family, he also heaped praise on his son, Donald Jr, who has overseen the planning and construction of the development so far, adding: “My mother would be very proud of the job that Don has done. He’s done a fantastic job.”

His flamboyant side soon reappeared as he talked of the latest American series of the Celebrity Apprentice and asked one of his executives to bring him a copy of People magazine with winner Bret Michaels on the front, showing off one of his many successful ventures.

He also joked with photographers, waving his hands around before pulling his trademark “You’re Fired” pose from the programme.

As the conversation turned back to golf, Trump admitted he had a “pretty low” handicap, rumoured to be around four, but added: “Some day I’ll hit the wall and it will start going up like a rocket.”

Trump, who plans to open the course in less than 18 months’ time, added that his perfect playing partners for the first tee would be Colin Montgomery and Sir Sean Connery. “I’d like to play with Colin. I’m a big fan of his, he’s a great Scottish golfer,” he said. “I’d love to have Sir Sean who has been a big supporter and friend of mine.”