MP Margaret Ferrier is facing growing calls to resign after travelling by train from London to Glasgow having tested positive for Covid-19.
She has been suspended from the SNP, with the party’s Westminster leader saying she should “do the right thing”.
Three SNP MPs have also added their voice to growing demands for Ms Ferrier to step down from parliament.
She has admitted travelling while having Covid symptoms and returning by train after testing positive.
Ms Ferrier has apologised and said she decided to travel to Westminster on Monday because she was “feeling much better”.
The MP for Rutherglen and Hamilton West spoke in the coronavirus debate in the House of Commons and said she received her positive test result that evening. She took a train back to Scotland on Tuesday.
Ian Blackford, the SNP leader at Westminster, told BBC Breakfast she should “reflect very carefully on whether she can continue as a Member of Parliament for her constituents”.
He said: “Nobody is above the law, nobody is above the regulations” and added: “I am calling on Margaret to do the right thing.”
Glasgow East MP David Linden, one of Ms Ferrier’s former SNP colleagues, had earlier told BBC Question Time she “should resign” as an MP.
His fellow SNP MPs, Kirsty Blackman and Stephen Flynn, have also called for her to step down.
Ms Blackman tweeted: “I agree with David Linden. Margaret Ferrier must resign. Both David and Margaret are unparalleled campaigners for our party but in this circumstance David is right. Margaret’s actions cannot be overlooked.”
Mr Flynn retweeted Ms Blackman’s tweet, writing: “Impossible to disagree. The public will expect nothing less.”
SNP leader and Scotland’s first minister Nicola Sturgeon had earlier tweeted her support for the decision to suspend the MP from the party.
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.”
Meanwhile, Ruth Davidson, former Scottish Conservative leader, told BBC Newsnight: “She shouldn’t be an MP at all. That’s on her and if she had a shred of decency she would [resign],” she said.
Taking public transport after testing positive amounted to an “absolutely reckless endangerment of person and of life”, she added.
Ms 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 Scotland confirmed they had been contacted by Ms Ferrier, saying officers were “looking into the circumstances” and liaising with the Metropolitan Police Service.
The Commons said she did not inform her party whip until Wednesday afternoon and that one person was identified as a close contact and told to self-isolate.
Ms Ferrier could face a £4,000 fine for a first-time offence of coming into contact with others when she should have been self-isolating under a law that came into force on the day of her positive test.
Dave Penman, general secretary of the FDA union, which represents some Commons staff, said it was “such a deliberate and reckless act”.
He told BBC Radio 4’s Today programme: “It’s a complete disregard for others. Coronavirus is like any other health and safety issue in the workplace – we all have obligations to other people and anyone who recklessly endangers other people has to face consequences.”