Peter Bone, MP for Wellingborough, said it was one of the “worst” pieces of abuse he had received in his 11 years working in Parliament.
The father-of-three told how police had rung to urge him to check his youngest son Thomas, 15, was still in school, when they saw the photo.
Describing some of the horrific abuse MPs have had to face since the EU referendum, Bone said in the House of Commons on Friday: “One of the worst things that happened [to me] was some months ago.
”There was a picture of my youngest son being executed by Isis.
“They’d actually taken another child and mocked it up. But the police rang me up to say ‘where’s your son?’
“’Oh he’s still at school,’” Bone replied, before being told “you’d better check”.
Bone said he only had to dial 999 once in his first decade working as an MP, but “since the referendum I’ve had to call them three times”.
He revealed the windows of his constituency office had been smashed with bullet holes, said his wife had been sent death threats too, and spoke out about receiving “vile” and “unbelievable” abuse on Twitter.
He added bravely: “I wouldn’t change any of that and some of us will be getting enhanced securities but we have to deal with that sort of thing.”