He said in some countries, such as Finland, there are EIDs - electronic IDs - in place.
"So there are ways there and there might be new ways in the future. The key thing is, it's not for me or politicians to decide what's effective. That will be the job of a regulator, but it is possible," he said.
Sarah Green, acting director of the End Violence Against Women Coalition, said: "Surveys have shown that more than half of young people have seen online pornography by the age of 14, and that many see it without even seeking it out as links are shared on social networks."
NSPCC chief Peter Wanless said the easy availability to children of online pornography was of "deepening concern".
He added: "It can leave them feeling frightened, confused, depressed or upset. The number of ChildLine counselling sessions regarding porn more than doubled last year to over 1,100 with some young girls revealing they were being pressured to mimic scenes from adult films.
"Any action that makes it more difficult for young people to find this material is to be welcomed.
"The key will be making any system work effectively as we know foreign outlets are recklessly flooding the market with films that can be viewed by anyone without any age checks in place."