THE former senior Scottish Tory at the heart of a row over so-called ‘dark money’ has instructed lawyers following a BBC documentary about his political activity and business record.

Richard Cook, who was a Vice Chair of the Scottish Tories and a parliamentary candidate in Glasgow and East Renfrewshire, has engaged media law specialist Peter Watson.

Mr Watson said the BBC show was defamatory and “counsel have been instructed”.

However it is understood matters are at a preliminary stage, and no defamation action has yet been launched.

Mr Cook was behind a highly controversial £435,000 donation during the EU referendum.

The money was given by the mysterious Constitutional Research Council, which Mr Cook chaired, to the DUP in Northern Ireland, where donations are traditionally secret.

The money was then used by the DUP to buy pro-Brexit newspaper advertising outside Northern Ireland, principally in London.

Opposition politicians claimed it was exploiting a loophole in electoral law.

Last month BBC Northern Ireland’s Spotlight programme broadcast an investigation into the episode called “Brexit, Dark Money and the DUP”.

The show dwelled at length on Mr Cook’s business record in waste management, including a number of deals overseas.

SNP Westminster Ian Blackford raised the issue at Prime Minister’s Questions on July 4.

Under parliamentary privilege, he said: “The BBC has revealed that the former vice chairman of the Conservatives in Scotland was behind the DUP’s £435,000 donation during the EU referendum, and has ‘a trail of involvement in illegal activities and foreign money’."

Mr Cook remains the chairman of the Constitutional Research Council and describes himself as “an international adviser in waste management and energy”.

His legal adviser, Professor Peter Watson of Glasgow-based PWB Law, said: “The BBC documentary is defamatory. Counsel have been instructed and all who choose to repeat the allegations will also be subject to proceedings.”

A BBC spokesperson said: "We stand by our journalism. We are not aware of receiving any correspondence from Mr Cook's lawyers since the programme was broadcast.

"The programme was made in accordance with our editorial guidelines."