The comment appears to be a reply to another post that read: “Opportunity to kill a few globalists.”
A further screenshot displays a news article thumbnail in which Mr Mercer appears, captioned: “The next dead MP?”
“People should know the price of being an MP before criticising those colleagues who choose to step down,” Mr Mercer explained via Twitter.
“This all from one guy, in Plymouth. Threatens to kill me, skin me in salt (bit specific), has done recces of my home, and encourages others to ‘lynch’ me.
“Thanks to the Community Security Trust for bringing this to my attention, and doing your bit to look after brilliant Jewish colleagues like @RuthSmeeth.
“Think before you do things like this. We all have families - and for the record, colleagues get far worse,” he went on.
The CST, a charity that provides safety, security and advice to the British Jewish community, wrote in light of Mr Mercer’s post: “As @JohnnyMercerUK says, this thread relates to a series of vicious threats against him that CST researchers found in the course of our work, which we reported to the police and to Johnny Mercer's office.
“Extremism feeds antisemitism and endangers democracy - it is all one fight.”