The widow of one of the men killed in the Teebane massacre said her family had been left "sickened" after the memorial to the workmen was attacked for the second time in five weeks.
White paint was thrown at the stone column memorial erected in memory of the eight Protestant men murdered in the notorious 1992 attack.
Six others were injured when the IRA blew up their minibus at the Teebane crossroads between Omagh and Cookstown.
The victims worked for Karl Construction and had been returning from their job at the Lisanelly Army Barracks.
Just last month, vandals destroyed floral tributes laid for the anniversary of the deaths.
Jean Caldwell, whose husband Jimmy died in the attack, said she was sickened by the latest incident.
After visiting the damaged monument, the mother-of-two added: "I was totally shocked and felt sick standing looking at it. To think the scum of the earth could do that again.
"It's only five weeks since they pulled every flower off it, which they then threw across the road. We were trying to get our lives back to normal after the anniversary service, then this takes you right back again to the day the atrocity happened. My hands were shaking. Why have they such a hatred towards that memorial?
"I believe it's the same people targeting the memorial, and it seems to happen at the weekends. I couldn't get over they could stoop so low.
"Are they getting a kick out of it? It adds to the pain and it takes us back to the beginning.
"I have to tell my two daughters about this and it's going to be so horrible for them as well. To me that's where they drew their last breath, and it's sacred for us."
Grand Secretary of the Grand Orange Lodge of Ireland Drew Nelson also condemned the latest attack.
"This is a deplorable act," he said. "Such memorial tributes should be sacrosanct, and those responsible ought to be utterly ashamed of their actions. Their wickedness goes beyond the pale and is deeply hurtful and upsetting to the relatives of the deceased, who have no doubt been re-traumatised by such vile and reprehensible criminality."
Trevor Wilson, an Ulster Unionist councillor for the Cookstown area, said he was "disgusted" by the incident. "This is one of the worst attacks on the memorial I have seen," he added. "Those who have taken the time to throw paint over the memorial show utter contempt for the victims' families, who will be totally distraught."
DUP Assembly member, Ian McCrea said: "It beggars belief that there are those who will stoop so low as to attack a memorial to eight innocent men murdered by the IRA. I want to appeal to anyone who may have witnessed any activity to contact the police."