Caught in a storm over a British teenager's suicide, Latvia's huge social networking website ask.fm has pledged to make changes and "mature", though supporters say it's being made a scapegoat.

Since its launch in 2010, the site has won a vast audience worldwide with 70 million users posting banter and cyber-exchanges on profiles -- at times testing limits under the cover of anonymity.

But the death of 14-year-old Hannah Smith, who hanged herself this month in the fifth teen suicide linked to the site, has plunged ask.fm into the murky debate over cyber-bullying.

Friends said Smith had been taunted on ask.fm about everything from her weight to the death of her uncle, with unsigned messages telling her to "drink bleach" and "go die".

The website -- the brainchild of Latvian brothers Mark, 29, and Ilja, 35, Terebin -- has already been cited in connection with four other such suicides in Britain, Ireland and the United States.

Critics say it has created an environment -- in which both registered and anonymous users can post answers -- that too easily leads to abuse.

In a sharp rebuke, British Prime Minister David Cameron said such sites should "step up to the plate and clean up their act and show some responsibility," in comments to BBC television .

He called for a boycott, while Smith's father demanded the site be shut down.

On Monday, the Terebin brothers released a statement through the London law firm Mishcon de Reya promising to carry out a major clean-up and "mature" by January.

"In the light of recent events highlighting the impact online bullying and harassment can have on young people, we engaged professional advisors to conduct a full and independent audit of our site and its safety features," they said.

It pledged to hire more moderators, ban anonymous users from certain sections and set up a separate parent-information page -- but steered clear of any responsibility in the suicides.

"As the site grows we recognise that it must also mature and adapt not only to stay relevant and attractive to our users, but to promote a safe and respectful environment."

Even though new users have signed up, the number of page views plummeted by 40 percent in the last month, according to web statistics monitor Alexa.

Big advertisers including telecoms giant Vodafone and designer Laura Ashley have also pulled out, wary of negative publicity.

The slide in fortunes was swift, coming only two months after another co-founder, 25-year-old Klavs Sinka, touted the company's quick rise to prominence on a local television program in June.

"It's a typical success story: just five boys sitting in a flat eating dumplings and thinking and thinking until we came up with an idea we were happy with," he told the TV3 news channel.

Ironically, he conceded that "things are very changeable, and there's never a final victory when we open the champagne and live the easy life."

His words proved prophetic.

"Everything we say is being twisted by the media," he told local journalist Kristine Zilde, one of the few people to speak to the founders in recent days, in an interview aired on Britain's ITN news.

"I would say they are confused," Zilde told AFP, adding she thought "the pressure and the negative image they are getting doesn't seem fairto them."

Though Mark Terebin deplored the suicides as "a true tragedy", he bristled when a question posted on his own ask.fm profile last year asked why "you will not talk to the Irish people regarding the deaths" of the two Irish girls.

"Mass media is knocking on the wrong door. It is necessary to go deeper and to find a root of a problem," he said.

"Ask.fm is just a tool which helps people to communicate with each other, same as any other social network.

"Don't blame a tool, but try to make changes... start with yourself... be more polite, more kind, more tolerant of others... cultivate these values in families, in schools."

The Latvian IT Cluster, an umbrella group for young tech companies, has come to the site's defence.

"Ask.fm is showing good will and investigates the problematic situation, which indicates that they are neither fraudsters, nor law breakers," its board told AFP in a statement.

Local columnist Karlis Langins added: "I think it is just another case of parents blaming everything for their child's death and politicians reacting in a populistic manner."

"It is an easy way out because they have an easy target at which to point their finger."