GORDON Brown’s think tank Our Scottish Future and campaign group These Islands are among the groups “named and shamed for their secrecy” around who funds them.

The pro-Union Scottish Business UK and the Centre for the Union were also given the lowest possible score in a new report listing the transparency of various think tanks and campaign groups.

Pro-independence think tank Common Weal and campaign group Business for Scotland were both marked at the opposite end of the scale – but the Scottish Independence Convention joined the Unionist groups at the bottom.

Reform Scotland, the think tank chaired by former Labour first minister Jack McConnell, was also given the lowest possible grade.

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The scores come from a report by openDemocracy, which has graded think tanks from A to E in a newly published “Who Funds You” audit.

The news site said the audit showed that “more than a quarter of the money that has been donated to think tanks focused on the devolved areas of the UK can be considered dark money”.

However, the four Unionist groups given the lowest E grade do not disclose even how much funding they are in receipt of, meaning it is impossible to know the true figures.

Of Brown’s Our Scottish Future, the audit states: “The organisation publishes no information on its donors and lists a firm of solicitors as its main director. This makes it impossible to know for certain who controls or funds it.”

Of These Islands, the audit says: “Its staff regularly feature in the media, and their research has had an impact on debate at Holyrood, but there is no indication on its website of who supports it, what income it has or what purpose money was provided for.”

And of the Centre for the Union, which was incorporated in Scotland but mainly focuses on Northern Ireland, the report states: “According to Companies House, the Centre for the Union has one director, Ethan Thoburn, who lives in London.

"He is also a parliamentary assistant to a Conservative MP, and has connections to other right-leaning, Tory-linked organisations including The Bruges Group and Orthodox Conservatives.”

OpenDemocracy said in their report: “With passionate views on all sides of the many constitutional debates that are likely to run and run in the UK, it is more important than ever that the organisations that seek to play a role in influencing public opinion are open about who is funding them, if they are to be viewed as trustworthy actors.”

The SNP said the groups given the lowest E grade had been “named and shamed for their secrecy around donations and where their money comes from”.

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Tommy Sheppard (above) the party’s constitution spokesperson at Westminster, said: “What do Unionist groups have to hide about who donates to them and where their money comes from?

“It is important for the public to know this as these groups try and influence government policy and the future of Scottish politics.

“We have no idea who is backing the interests of these Unionist think tanks but the public deserve the right to know because of the considerable influence they can wield.

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“The Tories have had serious questions to answer for a long time on who they are funded by, they have been surrounded by issues with dark money and foreign donations for a very long time. Yet, still we do not have the answers to that very basic question – who funds you?

“It is about time the Tories and the Unionist groups associated with them open the books and show us who is lining their pockets. If not, they will raise even more questions than answers.”

OpenDemocracy’s full report can be downloaded and read here.