Vodafone is looking into a 'severe breach of rules' by staff after an offensive 'tweet' was posted on its official Twitter account, Vodafone UK.

The offensive 'tweet' was posted at 15:47 and deleted shortly afterwards.

Since then, the operator has sent out numerous apologies to its followers on the social networking site.

Vodafone reacted quickly to the breach and posted an apology, just under an hour after the original post, which said: 'We're really sorry. A severe breach of rules by staff in out building, dealing with that internally. Please keep your faith in us.'

Only this week the operator was used as an example of a company using Twitter for good customer services by BBC programme Working Lunch.

Followers of Vodafone UK on Twitter started 're-tweeting' and asking Vodafone what had happened and have speculated that a disgruntled employee created the post.

One follower said: 'Have I missed something???'

A Vodafone spokesman said: 'This afternoon an employee posted an obscene message from the official Vodafone UK Twitter profile. The employee has been suspended immediately and we have started an internal investigation. This was not a hack and we apologise for any offence the tweet may have caused.'