Nola Leach, the Chief Executive of CARE, was speaking after the NSPCC report found 53% of 11 to 16-year-olds have encountered lewd material online, nearly all of whom (94%) have seen it by the age of 14.
More than a quarter of that group (28%) had first been confronted with the explicit content when they were only 11 or 12.
Smartphones were a common way for children to access X-rated sites as 33% of those surveyed first saw pornography on a handheld device.
The survey also discovered it was more likely for children to find material accidentally (28%) than seek it out (19%).
The NSPCC said an entire generation of children was at risk of being "stripped of their childhoods" and "desensitised" through exposure to pornography at a young age.
More than three-quarters of children surveyed - 87% of boys and 77% of girls - felt pornography failed to help them understand consent, while the majority of boys (53%) and more than a third (39%) of girls saw it as a realistic depiction of sex.
Speaking on Premier's News Hour, Nola Leach said: "I do welcome the fact that in the Queen's Speech they announced measures about age-verification proposals which we've been talking about for a long time.
"We need by law to have family-friendly filters which are on by default, and above all we need the government to step up its game.
"We can't afford to do nothing. Now is the time to act."
And speaking on Premier Christian Radio Andy Drake, the director of YMCA Chelmsford which works with young people, said that in pornography: "You're not seeing love being shared by two consenting adults.
"You're seeing one adult - usually a man - using power, violence, force, to get what they want.
"That can send a very strong message, a very incorrect message, to a young person."
A Department for Culture, Media and Sport spokeswoman said: "Keeping children safe online is one of Government's key priorities.
"Just as we do offline, we want to make sure children are prevented from accessing pornographic content online which should only be viewed by adults.
"In the forthcoming Digital Economy Bill we will bring in legislation that will require companies providing pornographic material online to make sure they have a robust age-verification system in place, so that those accessing their websites are over 18."
Listen to Premier's Aaron James speaking to Nola Leach on the News Hour:
Listen to Premier's Aaron James speaking to Andy Drake:
