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The Conservatives have lost the North Shropshire seat they held for nearly 200 years to the Liberal Democrats in a by-election blow to Boris Johnson.
Winner Helen Morgan overturned a Tory majority of almost 23,000, declaring that the “party is over” for the PM.
The result follows a torrid week for Mr Johnson, who has faced criticism over Downing Street parties and a rebellion by his own MPs over Covid measures.
Tory MP Sir Roger Gale said the prime minister was on “last orders”.
“One more strike and he’s out,” he told BBC Radio 4’s Today programme, adding that the by-election “has to be seen as a referendum on the prime minister’s performance”.
Conservative Party chairman Oliver Dowden said: “I know that the voters of North Shropshire are fed up and they wanted to give us a kicking… We’ve heard that message loud and clear.”
But he added: “I don’t think this amounts to a sea-change.”
The by-election followed the resignation of Owen Paterson, the MP for North Shropshire since 1997, who was found to have breached parliamentary rules on lobbying.
In her victory speech, Ms Morgan, who won by 5,925 votes, said: “Tonight, the people of North Shropshire have spoken on behalf of the British people. They have said loudly and clearly, ‘Boris Johnson, the party is over.’
“Your government, run on lies and bluster, will be held accountable. It will be scrutinised, it will be challenged and it can and will be defeated.”
Fourteen candidates stood in Thursday’s by-election. Ms Morgan took 17,957 votes, with Conservative Dr Neil Shastri-Hurst amassing 12,032 and Labour’s Ben Wood coming third with 3,686.
The last-placed candidate, independent Yolande Kenward, received just three votes.
The collapse of the Conservative vote in a once true blue, pro-Brexit seat is disastrous for Boris Johnson.
The endless headlines about sleaze and parties, held in apparent breach of the government’s own rules, drove voters away from the Tories in remarkable numbers.
Now, the question is whether Conservative MPs lose confidence in their leader. Many of them have been in despair about recent events.
The readiness of Boris Johnson’s parliamentary party to defy his authority was shown this week when half of Conservative backbenchers voted against the government’s Covid measures.
No 10 may try to brush off this by-election as mid-term malaise, a protest vote that should be kept in perspective.
But just two years after winning an 80-seat majority for the Conservatives, some of Mr Johnson’s MPs may look at this result and ask if their leader is becoming a liability.
The North Shropshire result is the second by-election loss of a former Conservative stronghold to the Lib Dems since the 2019 general election. In July, the party seized Chesham and Amersham, in Buckinghamshire, with a 25% swing.
Earlier this month, the Tories held Old Bexley and Sidcup in a by-election following the death of MP James Brokenshire, but the majority was cut from nearly 19,000 to 4,478, with a 10% swing to Labour.
The North Shropshire seat has existed in some form since the 1830s and, until Friday, had always had a Conservative MP.
The by-election came just two days after Boris Johnson experienced his biggest rebellion in office, when 100 Conservative MPs voted against the government’s proposals to introduce Covid passes in England.
It also followed rows about a Number 10 Christmas party during lockdown restrictions last December and the prime minister’s appearance at a virtual quiz alongside two colleagues at about the same time.
Before that, there had also been a fine for the Conservative Party over the financing of Mr and Mrs Johnson’s renovation of the No 10 flat, and the fallout over Owen Paterson’s departure, with the prime minister admitting some fault over the latter.
Reacting to his party losing North Shropshire, Dr Shastri-Hurst said: “We are 11 years into Conservative government. Our elections are never an easy thing to do.
“But of course, we do need to reflect upon the result and I am sure as a party we will do that.”
But Liberal Democrat leader Sir Ed Davey, who is currently self-isolating after testing positive for coronavirus, said it was a “watershed moment in our politics”.
“Millions of people are fed up with Boris Johnson and his failure to provide leadership throughout the pandemic and last night the voters of North Shropshire spoke for all of them,” he added.
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