Boris Johnson’s Tories have suffered a humiliating by-election defeat as the Liberal Democrats secured a historic win in Chesham and Amersham.

Lib Dem Sarah Green is the country’s newest MP after winning the seat, which has been a Conservative stronghold since its creation in 1974.

The contest was triggered by the death of former Cabinet minister Dame Cheryl Gillan, who took the seat with a majority of 16,233 in the 2019 general election – some 55% of the vote.

This Conservative Party has taken people across the country for granted for far too long

The stunning result saw Ms Green defeat Tory Peter Fleet by a majority of 8,028.

Ms Green said she was “humbled by the faith you have placed in me” and promised she would hold the Government to account.

“This Conservative Party has taken people across the country for granted for far too long,” she said.

The victory saw Ms Green take almost 56.7% of the vote, with the Tories second, the Green Party in third with 1,480 votes and Labour trailing in fourth with just 622 votes, losing the party’s deposit in the process.

In her acceptance speech Ms Green said: “Tonight the voice of Chesham and Amersham is unmistakable. Together we have said ‘Enough is enough, we will be heard and this Government will listen’.

“This campaign has shown that no matter where you live, or how supposedly safe a constituency may appear to be, if you want a Liberal Democrat member of Parliament, you can have a Liberal Democrat Member of Parliament.

“If you wish to reject Conservative mismanagement and vote for a voice that will represent you and stand up for your rights then it is the Liberal Democrats who will continue to fight your corner.”

She added: “We will continue the work of holding this Government to account for letting Covid rip through the care homes. We will speak up for the three million people excluded from financial support throughout the pandemic and we will challenge Boris Johnson to be far more ambitious in tackling climate change, supporting our frontline workers and backing our small businesses.”

Lib Dem leader Sir Ed Davey said the result – in a so-called “Blue Wall” seat in the Tory heartlands – had “sent a shockwave through British politics”.

The scale of the defeat will ring alarm bells in Conservative Campaign Headquarters (CCHQ).

Major issues in the campaign included the HS2 rail line, which cuts through the constituency and the Government’s proposed planning reforms which have sparked fears about building in the countryside around the seat in the Chilterns.

Mr Fleet acknowledged the need to rebuild “trust and understanding” with voters and also suggested the Tories had been out-campaigned by the Lib Dems.

“Clearly this was a very disappointing result, not the result that I was expecting nor my team,” he told reporters.

“It’s an absolutely extraordinary result which must take into account the fact that the Liberal Democrat party didn’t just throw the kitchen sink at this constituency, I think it was the microwave, the table, the oven, the dishwasher, the dog, the cat and anything else that was lying around as well.

“And we should consider that when we reflect upon the extraordinary nature of the result.”