Alistair Carmichael has been the subject of a death threat over his Commons support for Syrian air strikes.
The isles MP has declined to comment, other than to say the serious nature of the threat led to a decision within the party that the matter should be reported.
Police in Orkney said it was carrying out inquiries following “reported items of communications” sent to Mr Carmichael’s office on 10th December.
“Inquiries are continuing and suitable safety advice has been provided,” a police statement read.
Meanwhile, a party statement sent from the Liberal Democrats described the threat as “abhorrent”.
“A threatening letter related to the recent vote on Syrian air strikes was sent to one of the constituency offices and was immediately reported to police. These kind of comments are abhorrent and it’s only right that the police investigate who is behind them.”
Earlier this month the isles MP set out his reasons for the controversial support of bombings against Da’esh forces in Syria, insisting the Lib Dems had reached its decision after “lengthy discussion and deliberation”.
He was one of 397 MPs to support air strikes following a lengthy 10-hour debate at Westminster. There were 223 votes against air strikes.