THE country’s leading anti-independence campaign is facing questions about disclosing its income to election watchdogs after the leak of a secret donor list.

Scotland in Union is being urged to explain why it has not disclosed big donations to the Electoral Commission despite the list suggesting it should have declared more than a dozen.

The Commission said it was now “reviewing the matter”.

Scotland in Union denied any wrongdoing and said it was confident it had complied with the Commission rules but was “awaiting clarification” on the issue.

Its lawyers said they were correctly advised by the Commission that donations did not need to be reported unless they were 'specifically given to spend on the General Election.'

The threshold for a publicly registered donation is £7500.

According to the leaked list, Scotland in Union had received 14 donations of more than £7500 by July 2017, yet none appear to have been registered with the Commission.

Of these, 12 were made during the so-called “regulated period” in the run-up to the last two general elections and the last Holyrood election, when Scotland in Union was registered with the Commission as a “non-party campaigner” in order to spend more than £10,000.

Electoral Commission guidance for all three elections stated non-party campaigners had to declare accepted donations of more than £7,500 and that these would be published.

According to the leaked list and Commission records, Scotland in Union received one £7500 donation during the regulated period before the 2015 general election, when its bosses were considering forming a new party, and spent £13,388 as a non-party campaigner.

It received another single £7500 donation in the regulated period before the 2016 Holyrood election, when it spent £25,670 as a non-party campaigner.

And it received ten donations above £7500, a grand total of £138,500, in the regulated period before the 2017 general election, when it spent £73,818 as a non-party campaigner.

Most of the money went on marketing research, media campaigns, rallies and voter material.

Almost all the donations before the last election were sums paid for auction lots - which must also be declared to the Commission - at a lavish dinner in Edinburgh in late 2016.

Lots included stays at safari lodges in Africa, skiing chalets in France and Switzerland, a polo festival in India, and a plethora of hunting, shooting and fishing events in the Highlands.

Scotland in Union’s leaked data shows it also received two further big donations - of £9,600 and £15,000 - in late 2015, which was outwith any of the regulated periods.

In addition, the data records seven donations of £7499, just £1 pound below the threshold for registration with the Electoral Commission, suggesting attempts to avoid publicity.

The SNP said Scotland in Union must account for the apparent discrepancies.

A spokesperson said: “Scotland in Union must be held accountable.

“As a registered third party during elections they must uphold the proper standards and ensure transparency when it comes to their big donations."

Scotland in Union formed after the 2014 referendum to resist a second independence vote.

The cross-party group lost one of its chief executive after just seven months last year, and last month a group of its former staff set up a pro-Brexit rival campaign, UK Unity.

Last week, Scotland in Union suffered a damaging security breach when a list of hundreds of secret donors and their contact details were leaked to pro-independence websites.

Wings Over Scotland, run by controversial Bath-based blogger Stuart Campbell, and the Bella Caledonia site received the “data dump”.

Both said it was packed with members of the aristocracy and landed elite.

Scotland in Union subsequently reported the matter to the police and the UK Information Commissioner’s Office, which enforces the safe handling of personal data.

An Electoral Commission spokesperson said: “We consider and assess possible breaches of the rules consistent with our published Enforcement Policy and we are reviewing the matter.”

Scotland in Union said some points put to it by The Herald were wrong, but refused to explain what it meant or identify any of the points in dispute.

A spokesman said: “This information is wrong. All financial support for our campaign is in accord with Electoral Commission guidelines

And in a statement, Scotland In Union’s lawyers said: “The reality is that our clients were advised correctly by the Electoral Commission that donations were not reportable at all unless they were specifically given to spend on the General Election. Our clients have never received any donations for this purpose. They have breached no electoral law and any allegation to the contrary is false and defamatory.”es.”