MP Margaret Ferrier is formally under investigation by London’s Metropolitan Police over reported breaches of coronavirus regulations.
The Rutherglen and Hamilton West MP confessed to taking a train journey from London to Scotland while knowing she had Covid-19.
Ferrier had already travelled south to attend Westminster despite having developed Covid symptoms and booked a test.
In a statement revealing her actions on Thursday, the nationalist MP confirmed she had reported her actions to Police Scotland.
Nicola Sturgeon has called on the parliamentarian to resign, with the SNP withdrawing the party whip on Thursday evening.
The First Minister described Ferrier’s conduct as a “monumental error in judgement” and “incomprehensible”, and expressed her personal fury at what the MP had done.
In a statement, the Met said: “An investigation is under way into reported breaches of the Health Protection Regulations 2020.
“On Thursday, October 1, a member of parliament contacted Police Scotland to report she may have breached legislation and guidance relating to Covid-19.
“This related to her actions earlier this week, including a train journey on Tuesday, September 29, between London and Glasgow, following a positive Covid-19 test.
“Following consultation with Police Scotland, officers from the Metropolitan Police, working with British Transport Police, are conducting an investigation into potential offences.
“The parliamentary commissioner for standards has been informed.”
Among the potential sanctions Ferrier could face is a £4000 fine for “recklessly” leaving self-isolation.