Jim Gamble, from Ceop has hit out at these sites as rival Bebo adopted the button. He said there was "no legitimate reason" why their rivals had not done the same.
Ceop, the UK law enforcement agency tasked with tracing online sex offenders - says its Report button receives 10,000 hits a month on other websites, clicking the button allows users to contact specially trained Ceop officers for advice. It also provides details of local police and links to 10 other sources of help including Childline.
A person that goes online with harmful intent - whether it's the bully or whether it's the paedophile - they know when they see it that there is an active deterrent here. Mr Gamble said: "Children can contact us if they are worried, they fear about someone's intentions.
"Parents can be reassured because they know this environment is appropriately managed, with engagement with authorities ranging from the police service, including Ceop, right the way through to Childline online.
"And the predator, the person that goes on with harmful intent - whether it's the bully or whether it's the paedophile - they know when they see it that there is an active deterrent here."
Several sites including Bebo, MSN Messenger and Facebook already give users the chance to alert staff to abuse, but now Bebo has gone further by adopting the Ceop Report button itself.
A Facebook spokesman said: "The safety of Facebook users is the top priority for the company, which is why we have invested in the most robust reporting system to support our 300 million users.
"We also work closely with police forces in the UK and around the world to create a safe environment. Our teams are manned by trained staff in two continents giving 24-hour support in 70 languages.
"We look forward to hearing about the experience of Bebo using the Ceop button and will take account of their experience in any future evaluation of our reporting systems."
On Monday, a poll of more than 2,000 young people by charity Beatbullying found that 57% had been harassed online using Windows Live Messenger. Nearly a third said they had been cyber-bullied on Bebo.
Earlier this year, in the first criminal case of its kind in the UK, 18-year-old Keeley Houghton was detained for three months in a young offenders' institution for harassing a woman on Facebook.
