At the same time, he described India as a great place, asserting that he is not angry with Indian leaders.
The billionaire from New York said that he called up his credit card company to find out whether their customer support is based in the US or overseas.
"Guess what, you're talking to a person from India. How the hell does that work?" he told his supporters in Delaware.
"So I called up, under the guise I'm checking on my card, I said, 'Where are you from?'" Trump said and then he copied the response from the call centre in a fake Indian accent.
"We are from India," Trump impersonated the response.
"Oh great, that's wonderful," he said as he pretended to hang up the phone.
"India is great place. I am not upset with other leaders. I am upset with our leaders for being so stupid," he said.
"I am not angry with China. I am not angry at Japan. I am not angry with Vietnam, India...all these countries."
Trump mentioned the fake call to India during his remarks on what he described as "crooked banking."
Delaware, is a hub for the America's banking and credit-card industry. Topping the list include Bank of America, Citibank Delaware, M&T Bank and PNC Financial Services Group.
"They are making a lot of money," he said.
"You can't allow policies that allows China, Mexico, Japan, Vietnam, India. You can't allow policies that allows business to be ripped out of the United States like candy from a baby," Trump said in his address.
"The manufacturing jobs are being stolen. Our jobs are being taken. We are losing at every front. There is nothing good. Our country does not win anymore. The jobs are being stripped. Factories are closing. We are not going to let this happen anymore," he said.
Trump said he has as many as 378 companies registered in Delaware, where the Republican presidential primaries is scheduled on April 26 along with several other states.
He is leading in polls against his other primary rivals.
In his speech, Trump praised Delaware's status as a tax shelter and slammed President Barack Obama for not using the term "radical Islamists" in the fight against terrorism.
"I want to run against crooked Hillary," he said, reiterating that a Trump vs Clinton race would bring the greatest turn out in the history of the American elections.
"We will stomp on Hillary Clinton no one's ever done."
He was also critical of Indian-American South Carolina governor Nikki Haley, who did not endorse him during the primary.
Delaware has 16 delegates. Trump has 845 delegates, followed by Ted Cruz (559) and John Kasich (148).