Police will pass the addresses on to the sites which will then be expected to monitor usage or stop offenders logging on.
Sex offenders will face up to five years in prison if they fail to hand over the details or provide a false email.
The proposal is one of a series of measures announced by Home Secretary Jacqui Smith to make it harder for child sex offenders to meet children online.
Another is the publication of the first UK Social Networking Guidance which provides advice about how to stay safe online.
Developed by representatives from the industry, charities and law enforcement agencies, it can be used by service providers, parents and children.
It will provide links to a range of agencies to allow users to report issues of abuse or seek help.
She also launched a new kitemark for setting a standard for filtering software for home computers.
"I want to see every child living their lives free from fear, whether they are meeting friends in a youth club or in a chat room," Smith said.
"We are working together with police, industry and charities to create a hostile environment for sex offenders on the Internet and are determined to make it as hard for predators to strike online, as in the real world."
Jim Gamble, chief executive of the Child Exploitation Online Protection Agency and The Association of Chief Police Officers' lead on child protection and combating child abuse on the Internet, said: "In the virtual world we offer a one-click-away facility to every young person online.
"One click that will allow them to report virtual attacks of a sexual nature such as grooming to specialist officers backed up by support from organisations such as the NSPCC.
"Through the same click they can similarly access a whole source of signposting to other sources of advice and guidance covering a range of harm.
"This is being offered to every service provider and through them to every young person while they are in the virtual world. We call on them all to act now and adopt it."
