Hip-hop mogul Russell Simmons has written an open letter to US presidential hopeful Donald Trump asking him to 'stop the bullish*t' and said that we was "becoming a major embarrassment."

Simmons, co-founder of Def Jam Records and a hugely successful businessman - and a longtime friend of Trump's, FYI - has taken umbrage to his pal's increasingly bizarre and right-wing statements, such as his desire to ban Muslims from the USA.

He penned an open letter to Trump via Global Grind, which opened: "Over 30 plus years you have been an amazing friend; endorsing my books, coming to my shows, flying me on your planes, your helicopters, and even allowing my family members and myself to stay in your house in Florida many times. So, it kinda pains me to know that my public statements about your candidacy have strained or ruined our friendship."

He continued, saying "My friends, both Muslims and Jews, are saying there are so many comparisons between your rap and Hitler’s, and I cannot disagree with them, Donald."

"Stop the bullshit. Stop fueling fires of hate. Don’t feed into the rhetoric created by small-minded people. You’re smarter and certainly more loving then you let on. The Republicans in power don’t like you any more than the Democrats in power, as they know you can’t be controlled, because you are your own man. You have been many people’s champ in the past, but now you are becoming a major embarrassment. I know the cheap seats are easy to play to, but you can get them just by being the man I have known for nearly 30 years."

Read the full letter here.