The warning comes after Westminster on whether or not to allow the Republican presidential candidate entry to the UK, after more than half a million people signed a petition that was launched after Trump called for all from entering the US.
A statement from the Trump Organization highlights the group's intention to pour £200 million to further develop Trump Turnberry in the coming years, as well as the group's plans to invest £500 million towards further development at the 1,400-acre Trump International Golf Links.
However, the statement warns, "any action to restrict travel would force The Trump Organization to immediately end these and all future investments we are currently contemplating in the United Kingdom."
Trump has a number of business interests in the UK, including Trump International Golf Links in Aberdeenshire and the Trump Turnberry resort in South Ayrshire.
The statement also says the move to ban Trump would "create a dangerous precedent and send a terrible message to the world that the United Kingdom opposes free speech and has no interest in attracting inward investment."
This would also alienate the many millions of United States citizens who wholeheartedly support Mr Trump and have made him the forerunner by far in the 2016 Presidential Election."
Trump has denied claims he is a racist, insisting he is "doing good for the Muslims" with his call to ban Muslims from entering the US.
Justifying his comments, he also claimed there were "places in London and other places that are so radicalised that police are afraid for their own lives".