A number of UK advertisers have pulled their business from the social network ask.fm, in the wake of the death of a British teenager bullied on the website.

Specsavers, Vodafone, Laura Ashley and charity Save the Children are among the organisations which have said they will no longer market their businesses on the site.

Last Friday,  Hannah Smith, 14, from Lutterworth in Leicestershire died by suicide after she was subjected to cyberbullying by users of ask.fm.

Her father, David Smith, has said those who run the website should face murder or manslaughter charges and has called for more regulation of social networking sites.

Although they must register with an email address, name and date of birth, ask.fm allows its users to send messages to each other without disclosing their identity.

The Latvian based website has also been linked to several cases of cyberbullying in Ireland, including the death by suicide last year of teenagers Erin Gallagher and Ciara Pugsley.

Ask.fm has described Hannah'ss death as a "true tragedy", and in a statement said it wanted to reassure all users and parents of users that it is committed to ensuring the site is a safe environment.

It said it has contacted the Leicestershire police and would be happy to cooperate with their investigation into the teenager's death.

It has also said that it would actively encourage its users and their parents to report any incidences of bullying, either by using the in-site reporting button or via its contact page.

The website has been repeatedly criticised for not taking the issue of cyberbullying more seriously.

Earlier, British Prime Minister David Cameron said said internet users should boycott "vile" websites which allow cyberbullying to avoid more deaths of young people who receive abuse online.

Mr Cameron said website operators must "step up to the plate" to ensure users are protected.