U.S. Republican presidential candidate Donald Trump has threatened to cancel over 700 million pounds ($1.4 billion Cdn) of planned investments in golf courses in Scotland if Britain slaps him with a travel ban.

The threat from Trump, owner of two golf courses in his mother's homeland of Scotland, comes as British lawmakers prepare to hold a debate on a petition signed by over half a million people calling for him to be barred from the country after his proposal to stop Muslims entering the United States.

The debate will be held on Jan. 18, but will not be followed by a vote. Only interior minister Theresa May can issue an order banning entry into Britain and Prime Minister David Cameron has said he does not favour barring Trump.

The Trump Organisation said in a statement that a ban would result in him pulling developments worth 500 million pounds at a golf complex in northeastern Scotland, and a 200-million pound revamp at a resort in the country's southwest.

"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," the group said in a statement.

Trump's comments on banning Muslims from entering the United States in December prompted international outrage and led to him being stripped of two Scottish honorary positions.

The proud, half-Scottish billionaire's once-harmonious relationship with Scotland was soured further when he was blocked by a top court in his bid to stop a wind farm being built near his Trump International Golf Links course in Aberdeen.