The Prime Minister has come under growing pressure to intervene to stop controversial Scottish Limited Partnerships being used as "fronts" for organised crime.
SNP Westminster leader Angus Robertson said the firms, whose owners can be secret, file no accounts and pay no taxes, were being used by money-launderers.
The Moray MP demanded a meeting with Theresa May to draw up a joint plan to tackle the misuse of SLPs amid growing cross-party concern in Scotland.
Speaking during Prime Minister's Questions and citing a number of revelations in The Herald and the Sunday Herald, Mr Robertson said: "Scottish Limited Partnerships were established by this House in 1907 and they are being aggressively marketed internationally, especially in Eastern Europe."

Angus Robertson MP

HeraldScotland: Angus Robertson has been backed to continue as SNP Westminster group leader
Mr Robertson added: "The International Monetary Fund has warned of the risk posed by SLPs in the fight against global money laundering and against organised crime.
"It is now a matter of public record that SLPs have acted as fronts for websites peddling child abuse images, and that they have been part of major corruption cases in Ukraine, Uzbekistan, Latvia, Moldova and include the arms industry.
"Now given the seriousness of this issue, the Prime Minister's commitment to deal with criminality but the lack of progress on SLPs, will she agree to meet with me to discuss a joint way forward?"
The SNP, Labour, Greens and the Liberal Democrats have all urged action to review SLPs, which Herald research shows account for two out of three of Britain's most opaque corporate entities.

BACKGROUND: the secret bases of 25,000 Scottish 'tax haven' firms

Prime Minister Theresa May

HeraldScotland: UNDER FIRE: Theresa May
In the Commons Mrs May defended the Government's track record on tackling crime, pointing to the creation of the National Crime Agency - Britain's version of the FBI - as a sign of its commitment.
She said: "You raise issues around criminality and investigations into criminal activity that has taken place, and you talk about the issue of websites peddling child abuse and child sexual exploitation.
"It is precisely in order to increase our ability to deal with this criminal activity that we've created the National Crime Agency, that we have been ensuring that we have been working on other issues with the City like money laundering, and we are looking at the whole question of how we can ensure that we are taking effective action on criminal activity.
"He keeps saying will I meet with him, as he knows I do meet with him on occasions, I'm always happy to meet him. But if he wants to talk to me about dealing with criminal activity then I will be able to tell him about the work that has been done over the last six years under this Government in terms of the National Crime Agency, working with the City on money laundering, and enhancing our ability to deal with exactly the sort of criminal activity he's talking about."

Oxfam welcomed Mr Robertson's intervention at Prime Minister's questions. The charity's Scottish head, Jamie Livingstone, said: “We very much welcome this issue being raised because we are deeply concerned at the reported abuse of SLPs.“SLPs are insufficiently transparent and this could be helping those who want to dodge tax. Oxfam cares about tax dodging wherever it happens because we know it is the poorest people who lose out most.
“The misuse of SLPs risks tarnishing Scotland and the UK’s reputation at a time when our leadership on the issue of tax transparency is urgently needed.
“We hope the Prime Minister will ensure SLPs are reviewed and any loopholes closed as quickly as possible.

Mr Livingstone added: "In fact, the upcoming Criminal Finances Bill creates a timely opportunity for action and we would urge the Prime Minister to use this Bill to back up the Government’s strong words on tackling tax avoidance with real action.” 

Jamie Livingstone, Oxfam

HeraldScotland: Jamie Livingstone

The charity has called for cross-party support for addressing this issue in Scotland. It said more than 2,000 people have written to the leaders of the five parties represented at the Scottish Parliament and David Mundell MP, the Secretary of State for Scotland, backing its campaign.

This has attracted the support of First Minister Nicola Sturgeon, Scottish Labour Leader Kezia Dugdale, the Co-Convenor of the Scottish Greens Patrick Harvie and the Scottish Liberal Democrat Leader Willie Rennie.