Stephen Kerr has apologised after calling Murdo Fraser's leadership campaign "awful".
The senior Conservative MSP publicly backed his ally's bid but accidentally posted his concerns in a WhatsApp post.
“I’m beginning to wish I’d nominated Meghan," he wrote, in reference to Mr Fraser's leadership rival and Tory deputy leader, Meghan Gallacher.
Mr Kerr has reasserted his support for Mr Fraser and said his comments were taken out of context, calling the incident "regrettable".
Several messages were published on Mr Kerr's profile as a status update, rather than a direct message, allowing his contacts to view his doubts about Mr Fraser's campaign.
One statement said: "Murdo's campaign is awful".
After the statement were posted online, Mr Kerr reaffirmed his support for his colleague saying he was "certain" Mr Fraser' was the "leader we need now".
Mr Kerr publicly stated: “In a private conversation, in comments taken out of context, I expressed some concerns about one aspect of an upcoming event," he said in a statement.
"The person with whom I was having the private conversation is a close friend.”
Mr Kerr said he was "certain" Mr Fraser was the "leader we need now".
A spokesperson for Mr Fraser said: "Stephen has apologised to Murdo for his comments which he says were taken out of context, and is clear that Murdo is the best candidate for leadership."