The United Nations has blacklisted Scottish "tax haven" firms after uncovering fraud in its global aid programme.

In a major blow to the corporate reputation of both Scotland and the United Kingdom, UN officials have banned four anonymously owned limited partnerships or SLPs from bidding for their contracts.

The UN Development Programme or UNDP, which is responsible for a multi-billion dollar effort to fight poverty, has also debarred individuals who are nominally in control of scores of similar entities.

Its actions will pile on pressure for reform of SLPs, which were dubbed "Britain's home-grown secrecy vehicles" by anti-corruption group Transparency International.

The UNDP imposed five-year bans on all four SLPs, citing "fraud" or "fraud and collusion" as grounds and listing the formal sanction as "debarment".

All four businesses had been bidding for contracts in the former Soviet Central Asian republic of Uzbekistan, ranked as one of the most corrupt nations on the planet.

READ MORE: Questions as Uzbek president grants tax breaks to anonymous Scots firms

None of the sanctioned SLPs, which are registered alongside thousands of others at addresses in Edinburgh and Douglas, South Lanarkshire, have complied with rules under which they should have named their true owners by last summer.

This week a major new report from Global Witness, another anti-corruption group, found more than a third of SLPs had not even begun efforts to identify a "person of significant control", or PSC, a year after they were supposed to do so.

SNP MP Alison Thewliss has been campaigning for tougher reforms of SLPs, which are regulated under a part of Scots Law that has not been devolved. No SLP has ever been prosecuted for failure to reveal its owners.

HeraldScotland: SNP MP Alison Thewliss said "sanitary protection products are not an optional luxury"

Alison Thewliss MP

Ms Thewliss said: "It is encouraging that the United Nations are taking action against companies and directors, but it demonstrates clearly that the abuse of limited partnerships for fraud and collusion is a global problem."

But she added: "It’s disappointing that the UK Government aren’t being as proactive.

"Companies House is massively under-resourced, and that next to no enforcement action has been brought against those who choose to flagrantly flaunt the rules with respect to limited partnerships. We have a global responsibility to clear up the nefarious activity that’s originating on our own doorstep."

READ MORE: Global Witness: Scots 'tax haven' firms still mired in secrecy

Anti-corruption investigators believe that that many of the numerous SLPs active in Uzbekistan are fronts for officials or entrepreneurs who have no link to Scotland.

Private agencies have been selling ready-made SLPs and other UK corporate as 'ghost firms' across the former USSR and beyond, advertising them as 'offshore companies' whose owners can be secret, pay no tax and file no accounts.

HeraldScotland:

An internet advertisement for SLPs

The Herald has previously revealed that SLPs and English limited liability partnerships (LLPs)_ which have failed to reveal their owners have been buying chunks of Uzbekistan's lucrative cotton industry.

HeraldScotland:

The UNDP sanctions are against SLPs called Special Alliance Partnership, Investment Affairs, Trident Asia and Five Star Commercial Services. They are all registered either at a mail drop in Douglas, South Lanarkshire, or a flat in Edinburgh's Montgomery Street. Both addresses, essentially mail drops whose owners know nothing of the activity of businesses they host, are home to SLPs which have featured in some of the biggest money-laundering or fraud scandals of recent years. All four sanctioned SLPs have failed to file a person of significant control.

HeraldScotland:

The Douglas address

The UNDP also sanctioned some English LLPs and numerous individuals, including Uzbek citizens and a series of overseas directors or named persons linked with multiple companies.

These included people Matthew Bradley, a Belizean national who is the person of significant control of some 20 SLPs. Also sanctioned were Matthew Stokes and Alastair Cunningham. Along with Mr Bradley, these men are directors of the usually untraceable offshore corporate partners of hundreds of SLPs registered in Douglas or Montgomery Street. The Herald was unable to contact the named sanctioned individuals before publication. It is not uncommon for the directors or even named persons of significant control to have no knowledge of any activities carried out by businesses formally under their influence.

HeraldScotland:

The Montgomery Street, Edinburgh, address

The UN said it only sanctions vendors "where there is conclusive evidence of proscribed practices". Public filings show the SLPs sanctioned as bidders for aid contracts in Uzbekistan in 2013 and 2014. No further details were revealed about the investigation carried out by the UNDP.

There is no way to contact the real owners of the shell firms sanctioned.

The UK Government this week ended a consultation on further reforms of SLPs.

The UN crackdown is just the latest scandal to involve limited partnerships or SLPs, which have been abused as part of some of the biggest money-laundering and fraud cases of modern times, including the $20 billion Russian Laundromat and the $1 billion Moldovan bank robbery.

READ MORE: How Britain enables routine, everyday corruption and fraud in the ex-USSR