Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.) says Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's suggestion the U.S. set up a database to register and track Muslims is "outrageous and bigoted."

The Democratic presidential contender took to Twitter to blast the GOP front-runner on Friday, adding that Trump "should be ashamed of himself."

What an outrageous and bigoted statement. @realDonaldTrump should be ashamed of himself. https://t.co/KcDIMEQTnT — Bernie Sanders (@BernieSanders) November 20, 2015

Trump sparked controversy following last week's Paris terror attacks by suggesting a database for U.S. Muslims, as well as special identification or warrantless searches to allow law enforcement to keep tabs on those of the Islamic faith.

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“I would certainly implement that,” he said on Thursday. “[The database] would stop people from coming in illegally. We have to stop people from coming into our country illegally.”

Trump says the measures are necessary to prevent terrorist attacks by Islamist militants such as the massacre in Paris, which left at least 129 people dead.

Trump also argued that such a registry would have the force of law and Muslims would be mandated to identify themselves.

“They have to be,” he said. “They have to be.”

Critics have pounced on the idea, likening it to Nazi Germany's treatment of minorities.

Trump has deflected questions about whether he saw such comparisons.

“You tell me,” Trump repeatedly responded when asked.

The other 2016 Democratic contenders have also denounced Trump's idea.

“This is shocking rhetoric,” tweeted Hillary Clinton, the party’s current front-runner for 2016, on Friday. “It should be denounced by all seeking to lead this country.”

“When you hear people like Donald Trump talking about wanting to do ID cards based on religion, what the hell is that?” asked former Gov. Martin O’Malley (D-Md.) on Friday. “I mean, how is that at all American?”

Several of Trump’s rivals for next year’s GOP presidential nomination have also criticized his remarks, including former Florida Gov. Jeb Bush and Sen. Ted Cruz (Texas).

This story was updated at 1:27 p.m.