Scotland's first minister says the actions of an SNP MP who travelled to Westminster despite experiencing Covid symptoms are "utterly indefensible".
Margaret Ferrier said she made the journey because she was feeling "much better" - but also returned home after getting a positive test result.
The Scottish National Party MP, who has been suspended by her party, said there was "no excuse for my actions".
First Minister Nicola Sturgeon tweeted her support for the decision to suspend the MP.
She said: "This is utterly indefensible. It's hard to express just how angry I feel on behalf of people across the country making hard sacrifices every day to help beat Covid.
"The rules apply to everyone and they're in place to keep people safe. @Ianblackford_MP is right to suspend the whip."
One of Ferrier's former SNP colleagues, Glasgow East MP David Linden, has also said she "should resign" as an MP.
Ferrier said she took a test on Saturday after experiencing "mild symptoms", but travelled to London on Monday as she felt better.
The MP for Rutherglen and Hamilton West spoke in the coronavirus debate in the House of Commons on Monday, and said she received her positive test result that evening.
She then took a train back to Scotland on Tuesday.
Ferrier said she had informed the police and that she deeply regretted her actions.
"I travelled home by train on Tuesday morning without seeking advice. This was also wrong and I am sorry," she said.
"I have been self-isolating at home ever since."
Police confirm investigation
Police Scotland confirmed they had been contacted by Ferrier, saying officers were "looking into the circumstances" and liaising with the Metropolitan Police Service.
The SNP's Westminster leader Ian Blackford said he had spoken to Ferrier, who accepted that what she had done was wrong.
He said: "Margaret will be referring herself to the parliamentary standards commissioner as well as the police. I am tonight suspending the whip from Margaret."
House of Commons Speaker Sir Lindsay Hoyle wrote to MPs on Thursday evening to say he was informed after Ferrier told the SNP whip on Wednesday afternoon that she had tested positive for Covid-19.
"The House authorities immediately took all necessary steps in line with their legal obligations and PHE [Public Health England] Guidance," he wrote.
"On the basis of the information supplied to the contact tracing system, only one individual has been identified as a close contact in relation to this case and is now self-isolating."
A House of Commons spokesperson said the House's priority was to ensure the safety of those working on the estate.
'Dangerous and disgraceful' - train drivers' union
Labour MP Ian Murray said Ferrier had shown "astonishing recklessness".
"She has put passengers, rail staff, fellow MPs, Commons staff and many others at unacceptable risk," he said.
"To breach the rules twice is simply unforgivable, and has undermined all the sacrifices made by her constituents."
Train drivers union Aslef described her actions as "both dangerous and disgraceful".
The Scottish Conservatives' Holyrood leader, Ruth Davidson, said knowingly taking public transport after testing positive for Covid-19 put lives at risk.
Ferrier was one of the MPs who called on the prime minister's adviser, Dominic Cummings, to resign in the wake of the controversy over his visit to the north east of England during lockdown.
At the time, she said his actions had "undermined the sacrifices that we have all been making" and described his position as "untenable".