San Francisco - Twitter, we have a problem. The hit social networking and microblogging site that allows users to send brief messages to groups of friends or followers is failing abysmally at keeping its new devotees, according to a study released Wednesday by tracking firm Nielsen Online.

The study found that more than 60 per cent of new Twitter users failed to return the following month, said Nielsen Online researcher David Martin in a blog posting.

"Twitter's audience retention rate, or the percentage of a given month's users who come back the following month, is currently about 40 per cent," Martin said.

The figure would actually have been below 30 per cent were it not for the boost given to the site when US talk show queen Oprah Winfrey joined it earlier this year. "For most of the past 12 months, pre- Oprah, Twitter has languished below 30 per cent retention," Martin said.

Based in San Francisco, Twitter allows users to send and read other users' updates, which are called tweets and are limited to posts of up to 140 characters in length.

Lauded and used by celebrities like Britney Spears and Ashton Kutcher, as well as news organisations, companies and politicians, Twitter in recent months has been hailed as the hot new form of communication for the digital generation, but could quickly run aground, Martin predicted.

"Twitter has enjoyed a nice ride over the last few months, but it will not be able to sustain its meteoric rise without establishing a higher level of user loyalty," Martin concluded.

One user which is sticking with the service right now is the Center for Disease Control which is using several Twitter accounts to keep US citizens informed of the spread of swine flu and to dispense advice on how to avoid it.