TWITTER'S UK boss has apologised to women who have been threatened by "trolls" on the social networking site, as the company issued new rules on abusive behaviour.

Tony Wang, general manager of Twitter UK, posted a series of tweets yesterday saying abuse was unacceptable.

He wrote: "I personally apologise to the women who have experienced abuse on Twitter and for what they have gone through.

"The abuse they've received is simply not acceptable. It's not acceptable in the real world, and it's not acceptable on Twitter."

Twitter has updated its rules to make it clear that abuse will not be tolerated, and has put extra staff in place to handle reports of abuse.

The move came as Scotland Yard revealed it was investigating allegations by eight people of abuse on the microblogging site. Three claims involve incidents outside London.

Twitter faced criticism last week after three female journalists said they had been the subject of bomb threats on the site and two were threatened with rape.

The bomb tweet was sent to Guardian columnist Hadley Freeman, Independent columnist Grace Dent and Europe editor of Time magazine Catherine Mayer. The message was also sent to several other women.

In separate incidents, Labour MP Stella Creasy and campaigner Caroline Criado-Perez, who successfully fought for a woman to appear on £10 banknotes, were threatened with rape. Two arrests have been made in relation to those threats.

However, Steve White, of the Police Federation of England, said the problem was unpoliceable.

Criado-Perez said: "While I'm pleased they're listening, it's taken Twitter a week to come up with this.

"Right now, all the emphasis is on the victim, often under intense pressure, to report rather than for Twitter to track down the perpetrator and stop them.

She added: "The hard facts are that this will take time, investment and properly trained and paid staff - but it's crucial they get this right."

Creasy said: "I'd like Twitter to work with the police to be able to identify when particular accounts and particular users are under attack, and work quickly and effectively to protect them."