Donald Trump didn’t speak for an entire car journey after “screwing up” during a row with a Scottish farmer who was opposing his golf resort, his former project director has said.

Michael Forbes was refusing to move out of his home on the Menie Estate in Aberdeenshire to make way for a golf development by the former US president. The pair became embroiled in a David and Goliath battle when Trump called Forbes’ home “disgusting” and “a pigsty” at a press conference in 2010.

The businessman and media personality turned politician was hoping to build a new golf resort in the area, with plans going ahead with little controversy.

But, Neil Hobday, the former project director, said Trump’s comments about Forbes “changed everything” and resulted in huge opposition to the plans.

Speaking on new BBC Scotland podcast, Trumped, Hobday said Trump had been “flying high with opinion polls and everybody was supporting him” until the last question at the press conference: “Mr Trump how does it feel to be back in Scotland?”

“His response was so stunning, I thought I was having a nightmare,” said Hobday. “He went off on Michael Forbes. I thought ‘This is s***, this has ruined everything’. We got in the car to drive to Aberdeen airport where his plane was waiting.

“We said not a word the whole way back. He knew he had screwed up. Whatever goes on in Trump’s mind, nobody can figure it out. I couldn’t believe he did that, I was shaking with anger.

“We almost had a perfect outcome until that outburst. If I was Michael Forbes I would have reacted exactly the same way, I would have been furious to have been insulted in that way.”

Hobday added that Trump later tried to justify his remarks by boasting they had generated huge publicity for the golf course.

“He called a few days later and acted as if nothing happened. I told him it was all a bit heavy over here following the press conference,” said Hobday.

“He said ‘People in Brazil and Australia now know about my project. I just saved $10 million in advertising and PR’. That’s how he justified his outburst.”

Despite the Trump International Golf Links opening in 2012, Forbes still lives in his house after refusing to sell to developers.

Forbes’ portrait hangs in the National Galleries of Scotland and he received the Top Scot award in 2012 at the Glenfiddich Spirit of Scotland Awards.