Younger and younger children are accessing porn online, the Sun's agony aunt Deidre Sanders has told MPs.
She told an inquiry set up by MPs that young children had knowledge of sexual practices that used to be the domain of "bored 40-year-olds".
The former Home Secretary Jacqui Smith told the panel it was easy for children to access porn.
The cross-party inquiry into online child protection is chaired by Conservative MP Claire Perry.
Mrs Sanders has been calling on internet service providers (ISPs) to filter out adult content when they supply broadband to homes - with householders able to "opt in" if they want to access such material.
She believes that with new televisions being internet-enabled, tighter controls are needed.
The inquiry is looking at the extent to which children see pornography, at whether parents have enough tools to protect their children from it and at the arguments for and against ISP filters.
Mrs Sanders said it was clear younger children were seeing pornography.
"I am hearing all the time that it is escalating, notably since 2008, from younger and younger people," she said.
"Certain behaviours that I only used to have bored 40-year-olds asking me about goes now right down to the under-16s asking me about it."
She said she was behind the ideas about ISPs.
"All parents are not kind and caring. Not all parents would block sites," she said.
The former home secretary Jacqui Smith also appeared before the panel and told MPs her own research had showed her there was a lot of pornographic material available "without age restriction or the need to pay".
She made a documentary about pornography for BBC Radio Five Live after it was revealed that her expenses claims had included a bill for two pornographic films watched by her husband.
She told the MPs she was most concerned about young teenagers.
"We are talking about them being able to look at extremely hard-core pornography without having to pay or say their age," she said.
Justine Roberts, co-founder of parenting website Mumsnet, said: "It's more the type and nature of the porn and the fact that it is so hard core. The particular worry is that it skews ideas of what sex is all about."
Jerry Barnett, managing director of the UK's largest on-demand video pornography website Strictly Broadband, insisted legitimate members of the industry were properly regulated, with adult content behind a pay-wall.
He told the inquiry that the industry had been "decimated" by the increase of free online pornography but claimed stories of very young children accidentally discovering sites were mainly "mythical".
Next month, the inquiry panel will hear from internet experts and ISPs.
In June, when the Bailey review in to the sexualisation of childhood was published, the internet industry said it was aware of the problem of young children accessing inappropriate websites.
The Mobile Broadband Group said it supported "network based and device based solutions" to limit under-age access to online pornography.