SNP
"People in in Scotland are being let down," Peter Kyle said.
Scottish first minister admits it is not "helpful" that the SNP treasurer has been arrested.
Detectives have also interviewed Nicola Sturgeon's husband as part of the probe.
Douglas Ross said people should vote "tactically" to keep out the SNP.
The former first minister asked for "privacy" following the arrest of her husband.
Peter Murrell was taken into custody this morning.
By-election could be triggered after standards watchdog accuses Ferrier of "knowingly and recklessly" exposing people to the virus.
The new first minister wanted to demote his leadership rival.
He narrowly defeated Kate Forbes and will become Scotland's next first minister.
The SNP minister has doubled down on her controversial stance.