LBC
"It's invented, isn't it, James?" Labour's Yvette Cooper said.
"It's beyond embarrassing, it's wrong," the former cabinet minister replied.
Prime minister endures brutal grilling during LBC phone-in.
The broadcaster only stood down from his LBC show on Tuesday to run for parliament.
Between 1988 and 2003, the "promotion" of homosexuality was banned in English and Welsh classrooms.
'Where Are Those 40 Hospitals?': Health Secretary Victoria Atkins Skewered Over Tory Election Pledge
"You're doing this thing where you ask me to remember all the stats in my brain."
The PM managed to mix up a caller's name with where they live.
Radio station LBC was bombarded by questions from listeners asking when the country will go to the polls.
Sir Davd Lidington's comments drew criticism on social media.
The cabinet minister suggested the ongoing furore around the Tory donor is now "trivia".