* Ruling Conservatives defeated in parliamentary seat vote
* Liberal Democrats overturn 23,000-vote Tory majority
* Result viewed as backlash against PM Johnson (Adds Johnson comments)
By William James and Elizabeth Piper
LONDON, Dec 17 (Reuters) - Boris Johnson said on Friday he took personal responsibility for the loss of a Conservative stronghold in an election defeat that showed public dismay over a litany of scandals and stepped up pressure on the British prime minister from mutinous lawmakers.
The defeat was described as "a kicking" for his Conservative Party, substantiating fears among some that its reputation and electoral prospects are now suffering under Johnson.
The centrist Liberal Democrat candidate, Helen Morgan, won the North Shropshire seat by nearly 6,000 votes, overturning a 23,000-vote Conservative majority from 2019.
"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'," Morgan said in her victory speech.
"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."
Johnson, responding to the loss of a parliamentary seat his party had dominated for nearly 200 years, said he understood the frustration felt by voters over what he described as "a constant litany of stuff about politics and politicians".
He did not refer directly to the criticism he faces on several fronts, including over reports his staff held parties last Christmas when the country was in a COVID-19 lockdown, but said people were fed up with hearing about "stuff that isn't about ... the things that we can do to make life better".
"Clearly the vote in North Shropshire is a very disappointing result and I totally understand people's frustrations. I hear what the voters are saying in North Shropshire and in all humility I have got to accept that verdict," he told reporters.
"Of course I take personal responsibility."
The Conservatives had won every previous election for the mostly rural area of central England since the constituency was created in its current form in 1983. Conservative lawmakers have been dominant in the region for nearly 200 years.
Several lawmakers in the party had predicted the Conservative Party would lose the by-election, but many were surprised by the extent of the loss.
"Voters in North Shropshire were fed up and they gave us a kicking and I think they wanted to send us a message," Conservative chairman Oliver Dowden told Sky News. "We've heard that loud and clear."
However, Dowden said Johnson was still an asset and would lead the Conservatives at the next election, due in 2024.
Opinion polls show Conservatives, who still have a large majority in parliament, falling behind their main rivals, the Labour Party, following an outcry over lawmakers' second jobs, criticism of the way Johnson funded the lavish refurbishment of his flat, and a surge in COVID-19 cases.
"This has to be seen as a referendum on the prime minister's performance," Conservative lawmaker Roger Gale, a long-standing critic of Johnson, told the BBC. "The Conservative Party has a reputation for not taking prisoners. If the prime minister fails, the prime minister goes."
Another Conservative lawmaker, who asked not be named, said: "Serious questions now need to be asked on how the PM is going to get his house in order before we do it for him."
The North Shropshire vote was called because the incumbent Conservative resigned after he was found to have broken rules on paid lobbying.
The government tried to prevent that resignation by changing rules designed to stop corruption in parliament. It was forced to backtrack after a backlash over integrity and trust under Johnson's leadership.
British voters often use such by-elections to punish the governing party, but the scale of the Liberal Democrat victory suggests deep public dissatisfaction with Johnson's government.
Opposition politicians accuse Johnson of being a serial liar and incompetent leader, and some have demanded that he resign.
But despite growing discontent in the party, Conservative insiders say there is not yet enough of a groundswell against Johnson to dislodge him now, although they hope the vote will be a "wake-up call" for the prime minister to reset his agenda.
Any leadership challenge would require 54 of the party's elected lawmakers to formally register their lack of confidence.
"He needs to change now," a senior Conservative lawmaker said on condition of anonymity. "He needs to listen to the views of his party." (Reporting by William James, Elizabeth Piper, Kate Holton, Andrew MacAskill, Michael Holden, Editing by John Stonestreet, Catherine Evans, Angus MacSwan and Giles Elgood)
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