The pop icon blasted the Republican Presidential candidate during a radio interview – comparing him to Nazi leader Adolf Hitler.
The singer – who appeared alongside Trump is season nine of Celebrity Apprentice – compared the tycoon to Adolf Hitler as she criticised his attitude towards the LGBT community, especially considering that many of his employees are gay.
“The things that he says are appalling to me and shocking,” Lauper told San Diego’s Morning News last week.
“I was so shocked when he started to talk about the LGBT community, when in fact, people who did amazing work on his Celebrity Apprentice show were gay,” she revealed.
“You don’t talk about your employees like that ever.
“Even as a boss you have a responsibility for the people who work for you.”
Lauper also hit out at Trump’s daughter, Ivanka, for trying to sell her father as a pro-LGBT candidate.
Ivanka was widely credited with convincing her father to first use the term ‘LGBTQ’ during his July speech at the Republican National Convention.
He also discussed the mass the shooting at Orlando nightclub Pulse, which left 49 people dead.
“No matter what his daughter says, it has nothing to do with what that guy is selling,” Lauper added.
“That guy is selling inflammatory things that I have never in my whole entire life heard – except, you know, Hitler.”
Mr Trump was previously a lukewarm supporter of LGBT rights, but has changed his stance repeatedly during the campaign in a bid to appeal to the broad Republican base.
In recent months the Republican Presidential nominee has pledged to appoint justices to repeal equal marriage, come out in favour of North Carolina’s anti-trans bathroom law, and hinted at ‘religious freedom’ laws to permit anti-LGBT discrimination.