The Mail's stories involve the National Council for Civil Liberties, a group Harman worked for in the 1970s, the Daily Mirror reported. Her husband, Jack Dromey, a Labor member of Parliament, and former Health Secretary Patricia Hewitt also worked for the council.
The council at the time had an "affiliate," the Pedophile Information Exchange, which advocated reducing the age of sexual consent to 10, the Mail said. The Mail did not suggest Harman actually shared the exchange's views.
"They have accused me of being an apologist for child sex abuse, of supporting a vile pedophile organization, of having a relaxed attitude to pedophilia and of watering down child pornography laws. These are horrific allegations and I strongly deny them all of them," Harman said in a statement. "The editor and proprietor of the Daily Mail are entitled to their political views and they are of course entitled to oppose what I stand for but they are not entitled to use their newspaper to smear me with innuendo because they disagree with me politically and hate my values."
Dromey said the exchange had made an attempt to "infiltrate" the council and that he led the charge against them.
Avril Lavigne denies racism in 'Hello Kitty' music video
Joan Rivers refuses to apologize for kidnapping joke