Scottish firms are acting as fronts for international websites used to share child pornography.

A Sunday Herald investigation has discovered that secretive shell companies registered in Scotland are behind online file-sharing systems accused of enabling access to everything from images of young children being abused to "rape" videos.

The firms involved are Scottish limited partnerships, or SLPs, a once obscure kind of company now widely marketed across the former Soviet Union as a way for entrepreneurs to hide both their wealth and their identity.

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At least two such businesses registered in Scotland are formally hosting at least four so-called "cyberlockers", sites which appear to facilitate industrial-scale piracy of software, music, games, big TV shows, and Hollywood blockbusters.

These cyberlockers also host material featuring children under nine. Other forms of extreme pornography available featured rape and incest.

Our internet checks also uncovered links to piracy, with numerous mainstream films and television shows available, including movies currently on general release in cinemas, such as the latest Jason Bourne production.

The Sunday Herald has forwarded our findings to Police Scotland, which has launched its own investigation. After discussions with detectives we have decided not to publish the names of either the websites concerned or the Scottish-registered companies behind them in order not to alert the firms and impede the police investigation.

Detective Inspector Eamonn Keane, one of the country's leading cybercrime experts, has seen the links discovered by the Sunday Herald. He said: “Police Scotland is investigating this matter."

Keane stressed that there are numerous file-sharing systems available and that most of them do not facilitate access to any material that breaks indecency or child protection laws in Scotland or other countries.

He added: "But there are those sharing content that is criminal or close to criminal."

Cyberlockers are just the latest unethical or illegal business being fronted by Scotland's increasingly controversial limited partnerships.

The Sunday Herald last year detailed how such firms, sometimes based at modest council houses or virtual offices in provincial Scottish high streets, were used to launder proceeds of the alleged looting of $1bn from banks in Moldova, Europe's poorest country.

Similar SLPs, with secret partners formally registered in jurisdictions such as Dominica, Panama, the British Virgin Islands or Belize, were named in corruption scandals in Latvia, Ukraine and Uzbekistan.

Our sister paper, The Herald, has also revealed that they have been used as front companies for a variety of controversial online businesses, including those offering to write essays for students or pushing diet pills regarded in the UK as a scam.

Some cyberlockers linked to Scottish shell companies have already come to the attention of international campaigners.

A group based in Australia, Copy Control, has described one of the sites identified by the Sunday Herald as "a haven of illegal pornography" and campaigned for major credit card companies to boycott it.

The group, which is backed by the mainstream adult entertainment industry, claimed the cyberlocker concerned contained pirated software and movies, including legal porn, as well as images of children, animals and adults being sexually abused.

All four cyberlockers linked by the Sunday Herald to Scottish limited partnerships have published terms and conditions claiming to prohibit any illegal pornography or any images of children. The websites also say they do not allow users to upload copyrighted material.

However, such claims have been undermined by Copy Control which uncovered links entitled "rape medley" and "incest films" featured in promotions for $89 annual subscriptions to "Scottish" cyberlockers.

Law enforcement sources stress that such sites operate over a number of different jurisdictions, including those where child pornography or copyright protection are not taken as seriously as in Scotland.

The two Scottish limited partnerships linked to cyberlockers are registered at virtual offices in central Scotland and have no physical presence here. At least one of the sites in their name is also registered through a virtual office here. The cyberlocker sites themselves, while operating under the name of the Scottish shell companies concerned, give management addresses in other countries, such as Russia and South Korea.

The Sunday Herald shared some of its findings with the Federation Against Copyright Theft (FACT). Its director general, Kieron Sharp, said: "In principle there are many legitimate uses for cyberlockers, such as sharing photo albums or work related files.

"However, they are increasingly being used to illegally share copyrighted TV and film content. Popular cyberlockers receive millions of hits a day and are generating substantial profit through advertising or premium subscriptions and affiliate schemes – whilst the businesses and creators who put the time, effort and income into creating the content, are being short changed of their well-deserved revenue.

"What is even more concerning is that illegal piracy sites have also been found to be linked to other types of serious organised crime.

"Our investigations in the past have uncovered information that the individuals behind these sites are also linked to other illegal activity such as counterfeit pharmaceuticals and drugs and we continue to work with the police and other law enforcement agencies to ensure this criminality is combated."

An MP, Roger Mullin of the SNP, will this week seek an amendment to the UK government's Finance Bill to review Scottish limited partnerships amid growing cross-party concerns that the corporate structure, created under a Westminster law of 1907, is facilitating international tax evasion, money-laundering and cyber crime.

Children's tsar: "I applaud Sunday Herald"

Scotland's official champion of children's rights has called for those who access images of abused youngsters to be pursued with the same "vigour" as abusers.

Tam Baillie, Scotland's commissioner for children and young people, said: "We need to be clear: accessing pornography is not a victimless crime. The demand for it is leading to countless numbers of children being abused across the globe. The origin of the images doesn't matter, it is accessing them that creates the crime and fuels the demand for children to be used and abused."

Speaking after being alerted to the role of Scottish firms in fronting for websites where abuse files are shared, he said: "It is obvious that some adults will use any means at their disposal to access child pornography and the discovery that so-called 'cyberlockers' are being used for this purpose, is another illustration of the need to be always vigilant."

Baillie added: "Pornographic images have a longevity in the digital sphere and the impact of the abuse on children is devastating which makes it all the more urgent that we pursue those who access these images with the same vigour as we pursue those who abuse children, using whatever means we can.

"I applaud the Sunday Herald for shining a light on this issue."

Children's charity NSPCC last week revealed that Police Scotland had recorded 1900 child pornography offences over the last three years. The figure for the whole UK topped 21,600 in the same period.