Microsoft's Nicola Hodson said online child abuse content is "an evolving problem", making it "difficult to say whether anyone has done enough".
Ms Hodson told ITV News: "There is always much more to do, so we welcome the focus and we will continue to work hard on this area.
"We're very, very passionate about keeping children safe".
These are dramatic new steps which will make the internet safer and better for children, a leading Internet safety expert writes.
The search engines have stepped up to the plate - their reforms will help remove video child abuse content more quickly and comprehensively.
Former chief of CEOP Jim Gamble said the government must ask whether they are doing enough in the internet safety debate.