Mr Johnson also expressed his “absolute” sympathy for her family.

Chapman was jailed in 1996, aged 18, for raping two prostitutes and he was also suspected – though never charged – of carrying out other rapes against prostitutes in Ellesmere Port and Liverpool.

Asked about how Chapman had evaded checks, Mr Johnson said: “I think it is right that Merseyside Police actually respond to that.

“We have some of the most stringent laws governing sex offenders in the world and this terrible tragedy.

“We have to learn lessons from this, whether that is an issue about the monitoring of Chapman – and there is certainly an issue there – whether we need to do more, we have got this Child Exploitation and Online Protection Centre that is a very, very powerful organisation that we are seeking to give more powers to tackle this.”

Asked about how a convicted rapist could use social networking sites in this way, Mr Johnson said: “There is an idea we are talking to the Americans about. When you log on, if you are a convicted sex offender, that actually there is a way of flagging that up.

“What our people in the child protection and online protection agency do is actually go online themselves to actually try and lure in these people.”

Facebook itself was criticised for failing to do enough to protect children from online predators.

Unlike other sites, Facebook has not installed a help button for children to warn if they are at risk.

But a Facebook spokesman said: “The safety of Facebook users is our top priority. We have reporting buttons on every page of our site and continue to invest heavily in creating the most robust reporting system to support our 400m users.”