A trust accused of pouring "dark money" into Scottish Conservatives coffers is "not in any way mysterious", Ruth Davidson has told STV News.

The Scottish Tory leader denied the funds from the Scottish Unionist Association Trust (SUAT) were "dark money", insisting the party knows where the cash comes from and has "declared every penny".

SUAT is under investigation by the Electoral Commission over whether it is incorrectly registered as a donor.

It has gifted nearly £320,000 to the Scottish Tories since 2001, and an investigation by STV News found that a fifth of all declared donations to the party in the run-up to 2017's snap general election came from the trust.

Davidson pointed out that SUAT is separate from the Conservative party and said neither she nor her party have faced questioning in the Electoral Commission's probe.

It comes after another Scottish Tory donor, the Irvine Unionist Club, was fined £400 by the commission for failing to notify the UK's electoral body about a £100,000 gift shortly before the 2016 Holyrood election.

Following pressure and accusations of secrecy in the summer, SUAT disclosed its current trustees and address.

The Electoral Commission probe is looking into the group's status as an "exempt trust" - meaning it currently does not need to report donations in the usual way.

Speaking to STV's Holyrood editor Colin Mackay at Tory conference in Birmingham, Davidson was asked if she had been questioned as part of the inquiry.

The Scottish Tory leader replied: "The party hasn't and neither have I, no."

She continued: "First of all, there is no so-called 'dark money' - that makes it sound as if we don't where it's come from.

"In terms of the complaint that's been put in, it's that some properties that were sold in the 1960s, so 50 years ago, from which the sales were put into a trust, has been used to help out.

"The suggestion is that the trust, which is separate from the Conservative party, which registered under the Electoral Commission in 2001, should have had its registration changed into a different type of thing.

"That's not a suggestion that the Conservative party hasn't declared every single penny, because we have."

Davidson added she would be "happy to help" the Electoral Commission, saying: "We can't pre-judge what they're going to come out with, it's absolutely right that somebody independent is looking at that.

"Let's find out what the Electoral Commission say but in terms of what this is, it's not in any way mysterious.

"Some properties by supporters were sold in the 1960s - so, ten years before I was born - put into trust, invested and money from that comes to the party to help us campaign every year.

"We've declared 103 donations in the last 17 years."

Asked if the party was still accepting donations from the trust while the probe was ongoing, she said: "Look, we'll find out the result pretty soon so come back and ask me then."

SNP MSP George Adam said: "While Ruth Davidson is doing her best to obfuscate, she's failed once again to answer key questions that remain over the Tory dark money scandal.

"This is becoming a running embarrassment for the the Tories and as they try to hide from scrutiny then people will draw their own conclusions.

"This money has funded the election campaigns of Scotland's most senior Tory politicians - it's no trivial matter.

"Transparency over party finances is essential in a healthy democracy. The public has a right to know who helped put their politicians into office."

Scottish Labour have also called on Ruth Davidson to "come clean" about Tory donors, accusing them of "not playing by the rules".