Hannah Smith death: We'll name anonymous trolls, say Ask.fm founders – as advertisers pull out

The founders of the controversial website Ask.fm, which has been linked to the suicides of five teenagers, said they were working to improve its safety amid a growing backlash by advertisers and mounting public anger.

In an open letter Latvian entrepreneurs Mark and Ilja Terebin expressed sympathy over the death of Hannah Smith, 14, who took her own life last week after being subjected to a torrent of abuse by anonymous users of the site.

Prime Minister David Cameron called for a boycott of what he described as “vile” websites and said he was determined to take action to prevent further tragedies.

Meanwhile, advertisers including eBay, EDF Energy, The Sun, Laura Ashley, Specsavers, Vodafone and Save the Children withdrew advertising in a corporate stampede to disassociate themselves from Ask.fm.

In their letter the Terebin brothers, who founded the site in their native Riga in 2010 and have since watched it soar to 65m users worldwide, said they did not condone bullying.

“We are constantly working to improve our site including its safety features. We are currently working on a series of updates with more safety features and information,” they said.

“The vast majority of our users are happy teenagers who use Ask.fm to converse with their peers around the world about the things that interest them. Bullying is an age-old problem that we in no way condone – and while its evolution online is disturbing – it certainly is not unique to our site,” they added.

The brothers also said that in "extreme circumstances such as those we've experienced this week" they would be prepared to identify anonymous users via their computers' IP addresses and "ensure this information is accessible to the appropriate legal authorities."

Concern over the site emerged again this week after Hannah, 14, was found dead at her home in Leicestershire.

She had been urged by on-line bullies to cut herself and drink bleach. Her death followed that of Lancashire schoolboy Joshua Unsworth who died in March and two Irish teenagers, Ciara Pugsley, 15, and Erin Gallagher, 13, who took their own lives last year.

Jessica Laney, 16, was found dead at her home in Florida in December.

Many of the companies were unaware their products were appearing on the site, in which young people are encouraged to ask each other questions. Advertising is bundled up and sold on by agencies appearing as banners on the computers of users whose consumer habits are flagged up by imbedded “cookies” which track their interests.

Mr Cameron said parents and users should stop using the sites. “The people that operate these websites have got to step up to the plate and show some responsibility in the way that they run these websites,” he said.

Police in Halifax, Canada yesterday made two arrests in connection with the death of 17-year-old Rehtaeh Parsons, following a suicide attempt. A photo of her allegedly being sexually assaulted had been shared online.