MP Margaret Ferrier, who was suspended from the Commons for breaking Covid lockdown rules, has lost her seat in a recall petition.
A total of 11,896 out of the 81,124 eligible constituents in Rutherglen and Hamilton West signed the petition.
That exceeded the 10% threshold and means a by-election will take place.
Ferrier travelled to London and spoke in the Commons while awaiting the result of a Covid test in 2020 then got a train home after testing positive.
She was elected as an SNP member for Rutherglen and Hamilton West but was suspended from the party after the lockdown breach in 2020 and has since sat as an independent.
Campaigning in the seat has really already begun, with the SNP and Labour having selected candidates for an expected by-election months ago.
No date has yet been set for the vote, but the earliest it could happen is 5 October.
Ferrier had taken a Covid test on Saturday 26 September 2020 after noticing what she described as a “tickly throat”.
While awaiting her results, she went to church on the Sunday and gave a reading to the congregation. She later spent more than two hours in a bar in Prestwick, Ayrshire.
The next day, Monday 28 September, she travelled to London by train – which had 183 passengers on board – and spoke in the Commons before finding out a short time later that she had tested positive for the virus.
Ferrier decided to get a train back to Glasgow the following day, fearing she would have to self-isolate in a London hotel room for two weeks.
She was arrested and charged with culpable and reckless conduct in January 2021 and pleaded guilty last August. A month later she was ordered to carry out 270 hours of community service.
Labour and the SNP have both been campaigning in Rutherglen and Hamilton West for months already. But now the vacancy is official, expect things to kick up a gear.
This is a race which could have UK-wide ramifications, as a measure of Labour’s prospects under Sir Keir Starmer.
If he is to enter Downing Street, he needs to win this sort of seat – under 10% majority, sited in a former heartland – and a result here would build crucial momentum.
It is also a test of how flexible his party can be. Its UK-wide messaging is chiefly aimed at winning contests against the Conservatives in England, but the SNP is hoping to outflank it on the left in Scotland.
It is also an early test of Humza Yousaf’s leadership of the SNP.
He ran for the job as the Nicola Sturgeon continuity candidate, before ripping up key parts of her policy agenda. Can he replicate her record of electoral success?
The SNP is already putting independence front and centre of its campaign, and it will be interesting to see if the constitution continues to dominate as a political topic even as Labour endeavour to talk about just about anything else.
The Commons’ standards committee recommended in March that Ferrier should be suspended, a decision which was upheld by an independent expert panel after she lodged an appeal.
MPs then voted to suspend Ferrier from the Commons for 30 days, a decision which automatically triggered the recall motion.
The recall petition, which was the first to be held in Scotland, ran from 20 June to 31 July.
The seat became vacant at the moment the petition officer, who oversaw the count, informed the Speaker of the House of Commons of the result.
The date for the by-election will be set when parliament resumes in September.
Recent polling has suggested that the SNP’s lead over Labour in Scotland has narrowed in the wake of Nicola Sturgeon standing down as first minister and the ongoing police investigation into the SNP’s finances.
First Minister Humza Yousaf, the SNP leader, has previously admitted that the circumstances in Rutherglen and Hamilton West are “challenging” for his party – but that it has “solid support”.
But Scottish Labour’s deputy leader Jackie Baillie said people in the constituency had “made their voices heard and demanded change”.
She added: “For far too long the area has been failed – let down by two incompetent governments and left voiceless in parliament by their rule-breaking MP.”
Ms Baillie said a by-election should be held at the earliest opportunity so that “Rutherglen and Hamilton West can get the representation it deserves as soon as possible”.
The Scottish Conservatives’ deputy leader, Meghan Gallacher, said: “Margaret Ferrier’s constituents have delivered a very clear verdict on her reckless and selfish actions at the height of the pandemic.
“This by-election would have happened a lot sooner if she had done the right thing and resigned as an MP straight away.”
The Independent Parliamentary Standards Authority (IPSA), the body which regulates MPs’ pay and pensions, confirmed to the BBC that Ferrier is not eligible for any payoff for leaving parliament.