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Mr Murrell, the husband of former first minister Nicola Sturgeon, was charged in April of last year in a police investigation into SNP finances.

"Secrecy and evasion are hardwired into this SNP government, so the Scottish people will not be duped into thinking one overdue concession marks a change in culture."

The SNP has long rejected calls to end its effective ban, saying investment would be "better placed in areas of renewable energy".

The Tory leader also claimed that Scotland had "declined" under left wing parties and that the SNP had wasted millions on "independence propaganda".

"That is an astonishing industrial failure from the SNP."