The Scottish secretary has claimed the police probe into property deals involving an SNP MP will hurt the party more because it has held itself up as “exemplary”.
David Mundell said the controversy surrounding Michelle Thomson would have a “greater effect” because the Nationalists had claimed a “higher moral ground”.
The Edinburgh West MP has surrendered the SNP whip until the investigation into disgraced lawyer Christopher Hales – who acted for her before she was elected – is concluded.
She has also stood down as the SNP’s Westminster business spokeswoman.
Mr Mundell said: “If you hold yourself up as being exemplary citizens who are on a higher moral ground than everyone else, then when that is seen not to be the case, it has a greater effect.”
The episode has prompted calls from opposition politicians for the SNP to look into its vetting procedures.
Meanwhile, the SNP has now removed “The 56” merchandise – launched following the unprecedented election of 56 SNP MPs in May – from its website shop.
A Scottish Conservative spokesman said: “It would appear the SNP’s merchandise department has rather less confidence in Michelle Thomson than Nicola Sturgeon does.”