Margaret Ferrier attended a church service and gave a reading to the congregation the day after she developed coronavirus symptoms, it has been reported.
The Rutherglen and Hamilton West MP developed coronavirus symptoms and took a test on Saturday September 26.
She breached rules by travelling to London the following Monday and taking a train back to Scotland on the Tuesday after receiving a positive result.
The Daily Record newspaper reports that Ms Ferrier attended a Mass at St Mungo’s Church in Townhead, Glasgow on Sunday September 27.
She is said to have given a gospel reading from the altar.
The Archdiocese of Glasgow said: “For the good of the whole community, it is important that anyone who is required to self-isolate does so in accordance with the Government’s guidance, so anyone in that situation should not attend mass.
“It is disappointing if this has not happened but we would like to reassure people that we fulfil all the Government and church guidelines.”
The church’s website states public mass is limited to 50 people and those who are shielding, self-isolating or feel unwell should not not attend.
Coronavirus rules state that anyone who develops symptoms must self-isolate as they await their test result.
The SNP withdrew the whip from Ms Ferrier on Thursday evening after she admitted breaching the rules – saying she was “very sorry” for her mistakes.
Her admission provoked outrage from across the political spectrum, with many calling for her to step down as an MP.
Nicola Sturgeon said she spoke to Ms Ferrier and made it “crystal clear” she should resign as an MP, however she remains the member for Rutherglen and Hamilton West.