"We have seen cases where under-16s have been approached by people pretending to be same age, but who are grown adults trying to solicit young people for abusive contact," Mr Whittingham explained.He added that, although most messages in chatrooms were not inappropriate, a "small minority" had spoilt chat for people of all ages.
MSN UK's Matt Whittingham told BBC News Online it was not a decision they had taken lightly.
"We have been concerned about chatrooms for a while and reached a stage where we were no longer prepared to put up with inappropriate communication," he said.
People need to ask permission to be a "buddy" and they need to know the user's e-mail address to make a request, which means most children only have "buddies" who they know outside the internet.
They will also continue to make MSN Messenger free to users.
The only chat service available to MSN users in the UK will be the free instant messaging service, MSN Messenger, which is not so open and gives people more control over who they talk to.
Chatrooms on MSN's other global sites will either be supervised - or moderated - by an adult 24 hours a day, or will be on a credit card subscription-basis only.
Abusive contact Internet service provider Lycos has branded the action as "irresponsible" and fear children will move to other unmoderated chatrooms on the net.
Some have suggested that MSN may have economic reasons for closing down their chatrooms.
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Microsoft's internet service MSN is to cut back drastically its chatroom services because of concerns about child safety, it said.