A lawyer says he has been falsely accused of trying to have a sexual relationship with a suspected terrorist behind the 9/11 attacks.

Tim Jon Semmerling, a defence attorney and Middle East expert, is suing fellow lawyers who he claims spread “horrific” allegations that endanger his life and career.

The 56-year-old was appointed to defend Walid bin Attash, a Yemeni prisoner in Guantanamo Bay who has been formally charged with helping to train several of the 9/11 hijackers.

Mr Semmerling, who is gay, was warned by the CIA never to reveal his sexual orientation because of the views held my Islamic extremists regarding LGBT+ issues.

But in a federal lawsuit, Mr Semmerling claims rival lawyers told Mr bin Attash he was gay and was "pursuing a homosexual interest" with him. This triggered his sacking and left him a potential target in the Middle East, he alleges.

“They have hurt my career, these people, they have made sure I can never go back by outing me to Guantananamo Bay to work with any of the people down there,” Mr Semmerling told Fox 32.

Distress calls from 9/11 relive the trauma of the attacks

“How would that even be possible? If you meet with somebody down there, constantly around with cameras.

“I remember being in one, and the minute I took my shoe off, because my shoe was bothering him that day, and within a minute they had a guard in there telling me to put my shoes back on.

Walid bin Attash has been charged with helping to train 9/11 hijackers (Fox 32)

“So it couldn't even possibly happen. So that's what so absurd about it.”

One defendant named in the lawsuit is Cheryl Bormann, a defence lawyer who represented Mr bin Attash in 2012. She claims in court documents she is immune from any liability because she was providing legal services to a client.

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Mr Semmerling says she and others had a personal vendetta against him because Mr bin Attash preferred his work to theirs.