The party action came two days after officials suspended the party's national treasurer, who has threatened to sue leader Alex Salmond.

Margo MacDonald: Written warning

Lothian MSP, Ms MacDonald, has been a long-time critic of the party hierarchy.

SNP chief whip Bruce Crawford had written to all MSPs requiring them to attend the special group meeting in Edinburgh on Thursday.

He presented a report on the alleged breaches of discipline and recommended that Ms MacDonald be given a final warning.

But he failed to receive the necessary support from a third of members.

Amendement accepted

An amendment was proposed by Margaret Ewing that Ms MacDonald be given a written warning and that was voted through.

Meanwhile, party leaders have been seeking to play down the bitter internal row over the vote of no confidence and subsequent suspension of party treasurer Ian Blackford.

The successful international investment banker accused Mr Salmond of "control freakery" and of treating him and the party with "utter contempt".

Mr Blackford has consulted his solicitors, who he said took the view that he had a "clear-cut" case for defamation because the vote impugned his professional reputation.