U.S. Republican party presidential front-runner Donald Trump said on Sunday high salaries paid to chief executives were a "joke" and a "disgrace" and said these were often approved by company boards stacked with the CEO's friends.

Trump, a real estate mogul who has said he plans to use his net worth of $8.7 billion to fund his White House campaign, said in an interview with CBS's "Face the Nation" that it was hard to tackle the question of corporate pay because too many corporate boards lacked independence.

"It's disgraceful. Sometimes the boards rule but I would probably say it's less than 10 percent; and you see these guys making enormous amounts of money. It's a total and complete joke," he said.