On Sunday, Ms Oberman posted a picture of the Reverend and The Makers tweet about her and Ms Riley and wrote: “This band are going to be sued for spreading libellous unsubstantiated smears."
She called the band's tweet an "explicit statement" that she and Ms Riley would "be responsible for something terrible happening".
“These allegations cannot stand,” she wrote.
Ms Oberman and Ms Riley who have faced a deluge of antisemitic abuse over Twitter after criticising Jew-hate in Labour, have instructed Mr Lewis, who is Jewish, to help them take legal action against those who targeted them.
Mr Lewis represented the family of Milly Dowler in their phone hacking case against News of the World, and Jack Monroe, the food writer and journalist, in a successful libel suit against far-right media figure Katie Hopkins.
He confirmed he has made contact with the Reverend and The Makers' agent.
The band is fronted by Jon McClure, who is nicknamed "The Reverend."
