The lawmaker under fire for his "legitimate rape" remarks asked voters for forgiveness in a new campaign ad, as pressure mounted on Tuesday from fellow Republicans urging him to bow out of his US Senate race.
The sombre, 30-second spot begins with Missouri congressman Todd Akin looking directly at the camera and saying: "Rape is an evil act."
"I used the wrong words in the wrong way, and for that, I apologise," he continued. "As the father of two daughters, I want tough justice for predators. I have a compassionate heart for the victims of sexual assault, and I pray for them."
Akin, his party's nominee for the Senate race in the Midwestern state of Missouri, triggered outrage on Sunday when he said a woman's body can block an unwanted pregnancy during what he termed a "legitimate rape".
Astonished Republicans, including White House hopeful Mitt Romney who squares off against President Barack Obama in November's election, denounced the remarks as offensive and inexcusable, and the party leadership swiftly dropped all support for their Senate candidate.
But Akin has defiantly refused to bow out, despite a Tuesday deadline for him to voluntarily pull his name from the ballot.
"The fact is, rape can lead to pregnancy. The truth is, rape has many victims," Akin said in his ad.
"The mistake I made was in the words I said, not in the heart I hold. I ask for your forgiveness."
Akin is known for his vehement opposition to abortion, even in the case of rape, a position held by some pro-life conservative Christian groups.
"First of all, from what I understand from doctors, (pregnancy from rape) is really rare," Akin told Missouri's KTVI television in an interview that aired on Sunday.
"If it's a legitimate rape, the female body has ways to try to shut that whole thing down."
Republican National Committee chairman Reince Priebus blasted the remarks as "biologically stupid" and said if it was him he would drop out of the race.