The relative of one of the party’s MPs has been desperately avoiding media and refusing to answer his door in recent weeks.
A source said: “He has been going around associates, friends and family demanding to know who has reported him. He is absolutely livid as you can imagine.
“There has been a confrontation in a shopping centre – it has been causing all sorts of trouble. He thinks the police have been outside his house and he is not happy about getting caught up in this scandal.
“His MP relative is also keeping very quiet about the whole thing.”
A whistleblower has claimed senior party figures received donations but they then broke electoral law by failing to publish details. The allegations made in a letter to police and the Lord Advocate, the country’s chief prosecutor, are understood to involve tens of thousands of pounds.
Police Scotland have said they are still assessing the letter. Political parties are legally obliged to declare donations worth more than £500 with failure to do so a criminal offence.
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