Labour and the Lib Dems overturned Tory majorites of around 20,000 each to claim victory in yesterday’s by-elections (Picture: PA)

Rishi Sunak has been dealt two crippling blows as his party suffered historic by-election losses to the Lib Dems and Labour last night, with both parties overcoming Tory majorities of over 20,000 to claim victory.

Labour won Selby and Ainsty and the Lib Dems took Somerton and Frome with massive swings that will have Conservative MPs in even the safest seats looking nervously at their majorities.

But Mr Sunak was spared the prospect of being the first prime minister since 1968 to lose three by-elections on the same day as his party narrowly managed to cling to victory in Boris Johnson’s former seat of Uxbridge and South Ruislip.

Tory Steve Tuckwell held on with a majority of just 495, down from the 7,210 Mr Johnson secured in 2019.

At 25 years old, newly elected Labour MP Keir Mather is the youngest member of parliament- the ‘Baby of the House’ (Picture: Getty)

In Selby and Ainsty, 25-year-old Keir Mather will become the youngest MP in the Commons – the Baby of the House – after overturning a 20,137 majority.

The 23.7% swing from Conservative to Labour in the North Yorkshire seat to deliver Mather a majority of 4,161 is the second largest managed by Labour at a by-election since 1945.

In a speech after he was declared the winner of the by-election, Mr Mather said he ‘understood the enormity of what has just happened’.

‘We have rewritten the rules on where Labour can win. People have opened their doors to us and embraced our positive vision for the future,’ he said.

‘The people of Selby & Ainsty have sent a clear message. For too long, Conservatives up here and in Westminster have failed us, and today that changes.’

For the Lib Dems, a 29.0 percentage point swing in Somerton and Frome saw a 19,213 Tory majority turned into a 11,008-vote cushion for new MP Sarah Dyke.

Ms Dyke said she was ‘excited, exhilarated and most of all humbled’ at the result.

Lib Dem candidate Sarah Dyke has promised to be a ‘local champion’ for the area (Picture: Getty)

Asked what message the voters of Somerton and Frome had sent to Prime Minister Rishi Sunak and the Conservatives, Ms Dyke replied: ‘Clearly, they are fed up and they are frustrated, they are angry and they want a hard working Liberal Democrat MP.

‘They want a local champion and they have elected me to do that.’

Lib Dem leader Sir Ed Davey said the Somerton and Frome result showed his party was once again winning votes in its former West Country heartland.

‘The people of Somerton and Frome have spoken for the rest of the country who are fed up with Rishi Sunak’s out-of-touch Conservative government,’ he said.

The victory means Sir Ed has become the first party leader since Paddy Ashdown in the 1990s to win four by-elections.

Despite Labour’s success in North Yorkshire, the failure to secure victory in Uxbridge and South Ruislip in west London has led to a blame game among senior figures over the capital’s mayor Sadiq Khan’s plan to expand the ultra-low emission zone (Ulez) to cover outer boroughs.

Labour candidate Danny Beales had distanced himself from the policy, saying it was ‘not the right time’ to expand the £12.50 daily charge for cars which fail to meet emissions standards.

Despite the heavy losses, the Tories narroely managed to cling to victory in Boris Johnson’s former seat of Uxbridge and South Ruislip (Picture: Getty)

The defeat in the seat was dubbed ‘Uloss’ by a party insider in a sign of the unease at Mr Khan’s plan.

In his victory speech, new MP Mr Tuckwell said Mr Khan had cost Labour the seat.

‘It was his damaging and costly Ulez policy that lost them this election,’ he said.

‘This wasn’t the campaign Labour expected and Keir Starmer and his mayor Sadiq Khan need to sit up and listen to the Uxbridge and South Ruislip residents.’

Newly elected Tory MP Mr Tuckwell told reporters after his victory: ‘My campaign has been incredibly single-minded and it’s really been in complete opposition to Ulez from the outset.

‘That’s not me saying that, it’s not me that called the referendum on Ulez. It is the people of Uxbridge and South Ruislip.’

After saying ‘Sadiq Khan needs to listen’, he added: ‘Well, I think there will be Labour MPs in outer London boroughs who will be looking at this result tonight with sweaty palms.’

For Mr Sunak, the defeats happened as MPs drifted away from Westminster to begin their summer break, so he may be spared a clamour against his leadership.

The Prime Minister could attempt to reset his administration with a Cabinet reshuffle in the wake of the contests – Defence Secretary Ben Wallace has already signalled he will exit the Government, so there is a vacancy to be filled – although No 10 has publicly said there are no plans for a shake-up.

Mr Sunak may have decided the benefits of freshening up his team at this stage would be outweighed by the risk of it being perceived as a panicked response to an electoral setback.

Sir Keir Starmer said Keir Mather’s victory in Selby and Ainsty demonstrates the ‘demand for change’.

The Labour leader tweeted: ‘Congratulations @Mather-Keir, Labour’s new MP for Selby and Ainsty!

‘Last night, Selby and Ainsty made history. This incredible result shows how powerful the demand for change is.

‘Only Labour can deliver that change, and build a better Britain.’

The Tories’ victory in Uxbridge spared Rishi Sunak the prospect of being the first prime minister for 55 years to lose three by-elections in one night.