An MSP has quit the SNP, reducing the party's Holyrood majority to one.
John Wilson wrote to the First Minister informing him of his decision to leave the party days after Scotland returned a No vote in the referendum on independence.
The member for Central Scotland was critical of the SNP's stance over Nato membership.
It is understood he told Alex Salmond that he withheld his resignation until after the referendum campaign to ensure it did not distract from the debate.
Mr Wilson told The Scotsman newspaper: "I've made a decision to go, to resign from the SNP and the SNP whip. It was in terms of policy about Nato. There was a divergence of policy differences. There were a lot of issues. Things were happening with local branches and complaints about the headquarters. It was about internal democracy."
The paper reported that Mr Wilson will serve out his term at the Scottish Parliament as an independent MSP.
The SNP supports Nato membership provided it is not required to retain the Trident nuclear deterrent currently based at Faslane on the Clyde.
The policy saw the resignation of MSPs John Finnie and Jean Urquhart following a vote at a party conference two years ago.
The SNP now has 64 MSPs out of 127 voting members at Holyrood.
An SNP spokeswoman said: "We wish Mr Wilson well and accept his decision, which of course comes at the same time as more than 26,000 people have joined the SNP in recent days, overtaking the Lib Dems UK-wide and over doubling our membership.
"The SNP continues to have a majority in the Scottish Parliament. The SNP democratically decided our position on Nato at party conference two years ago, and we remain absolutely committed to ridding Scotland of Trident."
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