Deputy Labour leader Harriet Harman has condemned "horrible and untrue" allegations about her historic involvement in paedophile rights campaigns.
Mrs Harman said she was the victim of a "politically-motivated smear campaign" by the Daily Mail, saying she had "done nothing wrong".
"They have accused me of being an apologist for child sex abuse, of supporting a vile paedophile organisation, of having a relaxed attitude to paedophilia and of watering down child pornography laws. These are horrific allegations and I strongly deny them all of them," she said in a statement.
Mrs Harman and her MP husband Jack Dromey broke their silence after the newspaper ran a series of stories about their actions while officials at the National Council for Civil Liberties (NCCL) in the 1970s.
The body granted 'affiliate' status to the Paedophile Information Exchange (PIE), and is said to have lobbied for loosening of laws. Former health secretary Patricia Hewitt, who was also involved in the NCCL, has also faced accusations, but not commented.
Mrs Harman said: "In recent days I have been the subject of a politically-motivated smear campaign by the Daily Mail...
" This is not the first time the Daily Mail has made this horrible and untrue allegation. And, this is not the first time the Daily Mail has attacked me.
"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.
"I sincerely hope people won't believe these smears - I suspect even the Daily Mail doesn't believe them to be true. But given the seriousness and the aggression with which the Daily Mail are pursuing me, I feel that I need to put the facts in the public domain."
Mrs Harman denied that she had ever supported lowering the age of consent to 10, scrapping the law on incest, or sought to water down the law on child pornography.
Mrs Harman went on: "The Mail have tried to make me guilty by way of guilt by association.
"NCCL was an organisation which anyone could apply to join and indeed any organisation could apply to be "an affiliate" on payment of a fee. When I was at NCCL there were around 6,000 members and nearly 1,000 affiliated organisations of which PIE was one.
"Members and affiliates decided the organisation's policy at the AGM from year to year.
"I was aware that because NCCL opposed censorship and supported gay rights, paedophiles had sought to exploit that and use NCCL as a vehicle to make their arguments. But by the time I came to work for NCCL this vile organisation had already been vigorously challenged within the organisation. Jack Dromey was instrumental in that challenge when he took over the chair of NCCL in 1976."
Mrs Harman said she had gone to work for the NCCL because she had supported its work on gender and racial equality, and against domestic violence.
"Since being elected to the House of Commons in 1982 and during my times in Ministerial Office I have always championed the rights of those subjected to sexual abuse - especially women and children," she added.
"I hope The Daily Mail will stop this campaign of smear and innuendo against me. I have done nothing wrong and am guilty of none of their grotesque allegations."
Labour strategists are understood to have decided they needed to tackle the allegations "vigorously", as they did after the Mail criticised Ed Miliband's late father Ralph last year.
Mr Miliband heaped praise on Mrs Harman earlier today, insisting he did not "set any store" by the claims.
"I know she has a long and proud record of being on the right side of all of these issues," he said.
In a separate statement, Mr Dromey - a shadow home affairs spokesman - said the allegations were "beneath contempt".
"Sexual abuse of children is evil and I have always viewed paedophiles and any group associated with them as evil," he said.
"During my time on the NCCL Executive, I was at the forefront of repeated public condemnations of PIE and their despicable views. Then, when I was elected Chairman, I took them on.
"I personally chaired the NCCL Conference that, on my recommendation, refused to back by a massive majority a loathsome motion from a leading light in PIE calling on NCCL to support the so-called 'rights' of paedophiles.
"Indeed, my stand was denounced in a leaflet distributed by PIE to the delegates to the Conference.
"Like many organisations in the 1970s, NCCL had been infiltrated but that was the moment the tide was turned. I closed the Conference saying that we had to stand up for the rights of children not to be sexually abused and that adults guilty of abuse were the lowest of the low.
"I was then the first to argue that paedophiles could have no place in NCCL.
"As a lifelong opponent of evil men who abuse children, the accusations of the Daily Mail are untrue and beneath contempt."