US civil liberties groups have slammed plans by members of Congress to proscribe the Muslim Brotherhood as a terrorist group.

The Council on American Islamic Relations (CAIR) said the legislation, tabled by Republican senators Ted Cruz and Mario Diaz-Balart and supported by the Trump administration, could lead to a "witch hunt".

The bill, titled the Muslim Brotherhood Terrorist Designation Act, was submitted in January shortly before President Donald Trump took power.

It accuses the group of plotting a "grand jihad" to destroy Western civilisation from within.

"This potent threat to our civilisation has intensified under the Obama administration due to the wilful blindness of politically correct policies that hamper our safety and security," Cruz said in statement accompanying the bill.

He further accused the former US president of overseeing a "detente" with the group, which has renounced violence.

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The bill has been submitted to the State Department, headed by Secretary of State Rex Tillerson, which will decide on whether or not to designate the group.

Tillerson compared the Muslim Brotherhood to al-Qaeda in his confirmation hearing.

Al Jazeera approached members of the Brotherhood for comment on the move but they did not respond.

CAIR spokesperson Corey Saylor told Al Jazeera the ban was "highly probable given the number of Islamophobes who are directly advising Trump".

He said CAIR, which Cruz accuses of being affiliated to the Brotherhood, had no connection to the group but that he feared Muslim civil society groups could be targeted regardless if such measures passed.

"You have radical Republicans and extreme Islamophobes deciding US policy right now and I think that every minority is in for a very rough ride over the next few years," Saylor told Al Jazeera.

"Every Muslim organisation in the US has been subjected to extreme vetting at this point under both Bush and Obama. If they start coming after us, then the public should know that it's a witch hunt and nothing else. It has been investigated before."

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Hugh Handeyside of the American Civil Liberties Union (ACLU) said the move was part of a "long articulated plan by extreme Islamophobes to target and stigmatise American Muslims".

Those laws sweep up innocent individuals and organisations, and lack due process safeguards....it could have a tremendous effect on freedom of speech. Hugh Handeyside, ACLU

Fringe anti-Muslim groups had not succeeded in passing such measures under the Bush or Obama administrations but had found a willing ear in Trump, he added, further warning that ordinary Muslims may fall foul of the designation.

"Any move to designate the Muslim Brotherhood could enable the Trump administration to attack American Muslim civil society because that designation would open the door to using overbroad and unfair laws related to designated entities.

"Those laws sweep up innocent individuals and organisations, and lack due process safeguards ... it could have a tremendous effect on freedom of speech."

Conspiracy theories

The Muslim Brotherhood has long featured in the far-right discourse in the US that places it at the centre of a conspiracy to infiltrate government institutions.

Prominent Trump supporters, including members of Congress, have accused Hillary Clinton's close confidante Huma Abedin of secretly belonging to the Brotherhood.

Another adviser to Trump, Frank Gaffney, claims the Brotherhood has infiltrated the US federal government and that senior members of the Obama administration, including former CIA chief John Brennan, were complicit in helping to spread Shariah.

The move against the Muslim Brotherhood comes amid a Trump-initiated crackdown on Muslims entering the US.

Nationals of seven Muslim-majority states have been banned from entering the country even if they possess valid residency permits and visas.