The Prime Minister has said donations to the Scottish Conservatives are "accepted and declared in accordance with the law" following claims that a trust with links to the Tories may have been used to obscure the source of funds given to the party.
The Prime Minister was challenged by SNP Westminster leader Ian Blackford at PMQs over the Scottish Unionist Association Trust (SUAT), which has donated more than £319,000 to various Scottish Tory candidates and campaigns over the past 17 years.
Under current Electoral Commission rules, unincorporated associations are not required to register and declare where they receive their money from provided they donate less than £25,000 per calendar year to political parties and candidates.
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Following press coverage of SUAT's history of donations, the Electoral Commission said it was investigating whether any rules or spending limits had been breached. There is not currently any suggestion of wrongdoing.
However, the SNP has accused the Scottish Tories of accepting "dark money" and the MP Martin Docherty-Hughes has written to Ruth Davidson demanding that she be “honest with the electorate about who funds her party, and why it chooses to obscure donations.”
After PMQs, Mr Blackford “The Prime Minister cannot dismiss the scandal that the Scottish Tories have found themselves in regarding these dodgy donations.
“We need absolute transparency and someone must be held accountable - whether it is the Vote Leave campaign or the funding of the Scottish Conservative Party, our democracy cannot be bought.
“We know that Jackson Carlaw MSP, David Duguid MP and Douglas Ross MP all accepted donations from the Scottish Unionist Association Trust.
"The Trust has donated £319,000 to the Scottish Conservatives, yet there’s no information available about the people who currently manage the trust, no public accounts to indicate who its donors are, or what assets it holds.
“BBC Spotlight Northern Ireland has revealed the former vice chairman of the Conservative Party in Scotland - Richard Cook - was behind the DUP's £435,000 donation during the EU referendum, and has “a trail of involvement in illegal activity and foreign money.”
Mr Blackford added: “I gave the Prime Minister the chance to tell us what checks the Scottish Tory party had in place before accepting such large donations and ask, will she investigate the links between her Party and the trust with a promise to publish all donors and donations?"
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Responding to Mr Blackford's questions in the Commons chamber, the Prime Minister replied: "All donations to the Scottish Conservative Party are accepted and declared in accordance with the law, and the Scottish Conservative Party works with the Electoral Commission to make sure that is all done properly."
Following reports that the official Vote Leave campaign is set to be accused by the Electoral Commission of having broken electoral law by breaching its spending limits in the EU referendum, Mrs May said: "I'm not going to comment on what appears to be a leaked report which the government has not seen."
A spokesman for the Prime Minister said that rules around election spending were set by the Electoral Commission, which is "rightly independent".