Twitter's head of UK operations has apologised to women who have been subjected to threats of rape and violence on the social networking site and rolled out a set of measures designed to combat online abuse.

In a series of tweets, Twitter UK general manager Tony Wang said: "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.

"There is more we can and will be doing to protect our users against abuse. That is our commitment."

Earlier, Wang and the company's senior manager for trust and safety, Del Harvey, emphasised that Twitter users "may not engage in targeted abuse or harassment", and that the company was introducing a "report abuse" button on all of its platforms, with the feature having only been available previously on some smartphone devices.

Other measures announced included bolstering the team responsible for investigating spamming and working with the UK Safer Internet Centre to promote the safe and responsible use of the site.

"We are committed to making Twitter a safe place for our users," they said, adding: "We're here, and we're listening to you."

The announcement comes as the police confirmed they are investigating eight cases of violent threats made on Twitter.

This week two men were arrested after both Stella Creasey MP and Caroline Criado-Perez, who successfully campaigned for Jane Austen's portrait to be on the £10 banknote, received rape threats on Twitter.

The Guardian's Hadley Freeman, the Independent's Grace Dent and Time magazine's Catherine Mayer all received identical bomb threats on Wednesday.

Criado-Perez, 29, welcomed Twitter's response but said that the process for reporting abuse was time consuming and ineffective.

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

"Twitter's 'report abuse' button on the iPhone application goes through to the old reporting form. What we're looking for is an overhaul of the system which sits behind the button.

"The current process is lengthy, complicated and impossible to use if you're under sustained attack like I have been.

"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."

Steve White, of the Police Federation, said that the police were helpless when faced with the sheer scale of the problem and that companies needed to be proactive and find ways to stop threatening and abusive messages being posted.

He told BBC Breakfast: 'The organisations that run these social media platforms probably need to take a long, hard look, they need to take some responsibility.

'It's much like when you go into a shop - there are prevention measures within shops, whether it be security guards or things locked away that you can't get to, which is going to prevent crime, and I think social media sites need to think long and hard about being able to prevent it from happening in the first place.

'Crime has completely changed. Internet crime and e-crime, including the kind of trolling that we've seen this week, is hugely on the rise. Members of the public don't really understand what to do about it as well, so it goes unreported.

"We can't possibly deal with every single comment that someone doesn't like on these social media platforms, but I think the government's got to take a long, hard look at resources and have got to understand that there is a changing face of crime in this country, and the police service needs to adapt to that and the resources need to be there to do it."