This banner appeared over the A1 between the Bowes incline and the Angel of the North yesterday morning.
Nicola Morland and Angela Illingworth claim they discovered Steve Frazer had been two-timing them and decided to do something about it.
However, Steve's mother has now spoken out.
The Newcastle Chronicle reports she said: "He's not a mass murderer you know, it was just a stupid joke. He's not a bad lad, he just doesn't want to say anything. He does not want to take this any further."
She apparently spoke to reporters on the front doorstep, "while Steve watched from behind curtains".
She said he had spoken to one of the girls and "she knows she shouldn't have done it. I think it was maybe a stupid joke, but it's backfired. A bit of a cruel joke."
According to the Chronicle, it's believed Nicola was dating Frazer for a number of years, but when they split up, he started seeing Angela.
He then rekindled his relationship with Nicola, while continuing to see Angela. When they found out about each other, they commissioned the sign.