For years they were advertised for sale off the shelf as “zero-tax offshore companies”. Then they were damned, by Transparency International, as “Britain’s home-grown secrecy vehicles”.

Since close to the beginning of the century Scottish Limited Partnerships, or SLPs, have been the ghost firms of choice for criminals, corrupt officials and money-launderers around the world.

They are thought to be several thousand of them operating in Russia alone. SLPs were at the heart of that country’s notorious Laundromat, the biggest scheme to clean dirty money ever exposed.

Now they face potentially crippling new restrictions. From from Vladimir Putin, not the British Government.

The Kremlin hardman early this spring announced tit-for-tat sanctions on British corporate entities.

His crackdown on companies from “non-friendly” state - apparently unintentionally - has hit the often well-connected or wealthy Russians who use SLPs to own assets or businesses inside their own country. Specifically, SLPs, as UK registered entities, face unexpected legal hurdles, even if they are entirely Russian owned.

The issue has come to light thanks to a landmark court case over the control of Russia’s only major ice-free harbour in the Baltic, Kaliningrad.

The port’s operating company is privatised and run by a State Duma deputy from Putin’s Party, Andrei Kolesnik, who holds about a quarter of its shares.

Last year an SLP registered at a flat in an Edinburgh scheme took a 43% stake in this strategically important infrastructure.

Orneto Partners LP - which exists in the UK only on paper - sued to get access to accounts and other financial details.

Back in August a Russian appeal court judge turned this down, ruling the business had lost such rights as a corporate entity from an “unfriendly” nation.

The ruling suggests sanctions will hit SLPs and other UK shell companies, including both limited companies and limited liability partnerships or LLPs, even if they are openly and wholly owned by Russians.

The UK Government last month announced a new round of reforms it hopes will limit the abuse of SLPs - and other shell firms - under its economic crime bill. But it lags behind the Kremlin’s actions.

Oliver Bullough, author of Moneyland and Butler to the World, is an expert in Britain’s role in global money-laundering.

“We’ve known that Russian kleptocrats hide their wealth behind British shell companies for years but basically done nothing about it, to keep the roubles flowing in,” he told the Herald on Sunday.

“There's a bizarre irony to the fact that, after British politicians ignored this scandal for years, it finally took Putin to shut the door on this business.

“Though our enablers shouldn't despair -- kleptocrats from the rest of the world will still be clamouring for their services, even if the Russians aren't.”

Nobody knows for sure exactly how many SLPs are effectively controlled in Russia. The figure is guessed to be in the low thousands.

Ever since 2017 SLPs have had to name a person of significant control or PSC. Only 7500 or so have identified a human being. Of these, around 1556 were Russians and 1878 Ukrainians, according to research by corporate corruption expert Richard Smith. Fewer than 1000 were British.

Filings of this - or any kind - are rarely checked for accuracy by Companies House, Britain’s corporate registry.

It is also difficult to tell how many of the SLPs listed at the registry actually exist, or are trading in any meaningful way.

As the law stands, such firms can be dissolved and then re-animated at will.

The filing history of Orneto illustrates these quirks of UK corporate law. The firm was created in 2020. It named another SLP, Johnson and Brothers, as its “person of significant control”. Johnson and Brothers, which “owns” numerous other LPs, said it had no PSC. So there was no way of naming any individuals involved in operating Orneto Partners.

Johnson and Brothers, meanwhile, flickered in and out of formal existence while acting as the owner of Orneto Partners. It was dissolved in November 2020 before being re-registered shortly afterwards. And then it was dissolved again in January 2021 before again being brought back to life.

Orneto Partners was also twice shut down and twice re-animated. It took its 43% state in Kaliningrad Port on March 2, 2021, while, on paper at least, it did not exist. Two days later it filed a confirmation statement to Companies House as an active firm and a month later it lodged paperwork in which it said its previously announced dissolution had not, in fact, taken place.

This March, shortly after Putin’s full-scale invasion of Ukraine, Orneto Partners made a new filing. Its PSC, it said, was no longer Johnson and Brothers but a 28-year-old Russian national named Kirill Purim.

Kaliningrad news agency Russky Zapad said Kirill Purim - who runs several companies - was the son of Dmitri Purim, chairman of the board of the nearly century-old Russian shipping and transportation giant Sovfrakht.

There is no suggestion of any wrongdoing by Purim, or Kolesnik, or anybody at Orneto Partners. Their court case was civil, not criminal. Russian sources, such as Russky Zapad, say judges have effectively ruled that the port’s financial information is classified, a secret for its formally Scottish owner.

Scottish business lobbies have long argued that the abuse of SLPs is damaging the country’s corporate reputation.

For years the real owners of such firms were, in effect, able to remain anonymous, file no accounts and pay no tax, provided they operated overseas.

Over the years The Herald and Herald on Sunday have exposed scores of examples of SLPs being used as secrecy or money-laundering vehicles, for everything from internet scams to the bribery of Latin American presidents.

The Tories - before the latest ructions and resignation of Liz Truss - last month finally announced long-planned reforms of SLPs, including checks on the identity of their owners.

Lord Callanan, the minister for corporate responsibility, said: “This historic bill will ensure we safeguard the reputation of Scotland, and the UK more widely, as one of the best and most-trusted places in the world to do business. The reforms to Scottish limited partnerships in particular are hugely important. While we know they are used in a variety of ways for legitimate purposes — from venture capital to holding agricultural tenancies — there are still too many bad actors who seek to exploit their limited liability to carry out money laundering and fraud.”