Sex offenders could be forced to register their e-mail addresses and chatroom names, the government says.
The announcement coincides with Safer Internet Day
Home Secretary John Reid said he may make paedophiles put online identity details on the Sex Offenders Register.
Mechanisms would be set up to "flag up" approaches by them to sites popular among youngsters, he told the BBC.
One computer expert said this was a step in the right direction, but added internet identities could be changed "in a matter of seconds".
Mr Reid said: "We already have probably the toughest regime in Europe for identifying sex offenders.
"But although we are strong, we have to keep ahead of the game and I want to bring in stronger, broader powers to protect our children."
He told the BBC: "If we did that we would then be able to set up mechanisms that would flag up anyone using those addresses or those identities to make approaches and contacts through some of the very popular internet spaces which are used by kids."
Cliff Saran, technology editor of Computer Weekly, told the BBC News website: "I have about five e-mail addresses. It's easy to set up a new one in seconds... it's going to be hard to track that."
The same applied to chatrooms and networks like MSN, he added - "Come up with a suitable name, and off you go."
Nearly a third of young people have received unwanted sexual comment online or by text
Just 7% of parents know their child has been subjected to such material
4.2 million websites contain indecent images
100,000 websites contain indecent images of children
He said the government's move was a step in the right direction and the industry would co-operate - but opportunities would arise for organisations to market "premium" - allegedly untraceable - e-mail accounts.
If everyone had a single internet identity for life, like a National Insurance number, this would make it far easier to track people, he said. Child internet safety expert John Carr, of children's charity NCH, said: "This is a very welcome move.
"It will mean that we can extend the Sex Offenders Register regime into cyberspace and that will be a great comfort to many people."
Under present rules, sex offenders must list their name and address on the Sex Offenders Register for a period of years after conviction or even for the rest of their lives.
However it is feared that some continue to find a way around the existing system.
Last month newspaper reports said police forces across the UK had lost track of 322 convicted sex offenders. The News of the World claimed one paedophile who had breached register conditions had given his address as "woods" after moving from "a tent near Guildford leisure centre".
The latest proposal means their online identities would be treated in exactly the same way as their real name, a Home Office spokesman said.
Failure to divulge all the information required could lead to a jail term of up to five years.
Prof Allyson MacVean, director of the John Grieve Centre for Policing and Community Safety at London's Metropolitan University, said police should be able to search sex offenders' homes and computers.
"Internet addresses are so easy to make up and it doesn't give any sense of who the person is or where their location is," she told the BBC.
She said this was why the police needed access to sex offenders' computers without needing to apply for a warrant.
Mr Reid was visiting the headquarters of Ceop (Child Exploitation and Online Protection Cetnre) in London on Safer Internet Day, a worldwide event, organised by European Schoolnet, intended to raise awareness among parents, teachers and young people of the risks associated with use of the net.
Events are being held in 31 nations and a blogathon will record activities held as far apart as Australia and Canada.