MP Margaret Ferrier will face no further action from the Metropolitan Police after she travelled between London and Glasgow following a positive Covid-19 test.
Ms Ferrier had the SNP whip removed after it emerged she made the trip from Glasgow to the House of Commons while waiting for results of a test she took on September 26 and made the return journey after being informed she had the virus.
Amid mounting pressure for her to resign her seat, Ms Ferrier has held on and the Metropolitan Police has now said in a statement that regulations under which Ms Ferrier could have been punished were not in effect when she travelled.
According to a statement from Scotland Yard, the Rutherglen and Hamilton West MP's test occurred before September 29, when new regulations came into effect that could have resulted in a £10,000 fine being levied against her.
The statement said: "Officers considered possible offences including those under Reg. 11(2) of the Health Protection Regulations 2020 which relates to self-isolation requirement.
"However, on detailed examination of this new legislation, and following legal advice, it was concluded that this regulation is applicable only after September 28 2020.
"In this case the test occurred prior to September 29 2020 and therefore the regulation does not apply.
"As such, there will be no further action in relation to this investigation from the Metropolitan Police."
Ms Ferrier's case could still be taken further by Police Scotland.
The statement from Scotland Yard added: "We are in liaison with Police Scotland and have referred the matter to them for consideration."
Police Scotland said in a statement they are aware of the decision by the Metropolitan Police and "will now assess the circumstances and consult with the Crown Office and Procurator Fiscal Service before taking a decision on next steps".
Since news of her trips broke, the MP has faced increasing calls for her resignation, including from SNP leader Nicola Sturgeon, who has repeatedly called for her to stand down.
Labour leader Sir Keir Starmer and Scottish Labour leader Richard Leonard have also been among those pushing for Ms Ferrier – who beat Labour's Ged Killen for the seat last year – to go.
In an interview with The Scottish Sun, Ms Ferrier said she felt she was "hung out to dry" by the SNP, which withdrew the whip from her one hour after she released a statement detailing her actions.
She also said she had no intention of standing down.