British Prime Minister Rishi Sunak was dealt a major political blow on Friday as the governing Conservatives suffered a bruising in two key by-elections but averted a complete whitewash as the party held on to his former boss Boris Johnson's seat in London.

Thursday’s three-way by-election was widely pitched as a report card on the 43-year-old British Indian leader's handling of the economy and wider prospects as party leader going into a general election, expected in the second half of 2024.

The Tories' narrow victory in the suburban seat of Uxbridge, which they won by 495 votes, spared Sunak the humiliation of being the first PM for 55 years to lose three by-elections in one night.

Conservative Steve Tuckwell just about holding on to Uxbridge and South Ruislip, Johnson’s seat, until he stepped down in the wake of a parliamentary inquiry into party gate inquiry last month, was the only bit of good news for the party.

During a visit to Uxbridge soon after the results on Friday morning, Sunak said the victory there showed that the next general election was not "a done deal".

Asked what the defeats meant for his party, Sunak replied: "The message I take away is that we've got to double down, stick to our plan and deliver for people."

The Opposition Labour Party overturned a massive Tory majority of over 20,000 to decisively clinch the Selby and Ainsty constituency in northern England, a by-election triggered by the resignation of close Boris Johnson ally Nigel Adams.

"This is a historic result that shows that people are looking at Labour and seeing a changed party that is focused entirely on the priorities of working people with an ambitious, practical plan to deliver," said Labour Leader Keir Starmer.

With the big win, his namesake 25-year-old Keir Mather overtook Indian-origin Labour MP Nadia Whittome as the so-called “Baby of the House” to become the youngest member of Parliament. It will be a long wait, though, for him to take his seat in the House of Commons, which is now on its summer recess and resumes only in early September.

In a second bruising for the Sunak-led Conservatives, the Liberal Democrats swept the Somerset and Frome byelections in southwest England. Sarah Dyke, a Somerset councillor with a farming background, secured a dramatic victory by winning 21,187 votes, with Conservative Faye Purbrick left far behind in second place with 10,179 votes.

In her victory speech, Dyke thanked "lifelong Conservative voters" who had voted Lib Dem for the first time, as well as Labour and Green supporters who had "lent" their votes. She said the public had been "let down and taken for granted for far too long" by the Conservatives, with the government "too busy being a circus of chaos".

The by-election was triggered by the resignation of former Tory MP David Warburton, following allegations of drug-taking and sexual misconduct.

The Lib Dem leader, Sir Ed Davey, who had campaigned hard in Somerset, hailed his party’s "stunning victory”, which he said shows his party is on course to make a comeback in the region and that the country is "fed up with Rishi Sunak's out-of-touch Conservative government".

In London, the sole Tory win was largely attributed to anger against Labour Mayor Sadiq Khan over his plans to extend the Ultra Low Emission Zone (ULEZ) to outer areas of the UK capital. The policy has proved extremely divisive, and it meant the Tory candidate held on to the Uxbridge and South Ruislip seats by just 495 votes.

In his victory speech, new MP Tuckwell said Khan's "damaging and costly ULEZ policy" lost Labour the seat.?

Polling expert John Curtice said the Conservatives' vote share across the three by-elections showed the party was in "as deep an electoral hole as the opinion polls have been suggesting".

He added that its two defeats in Somerset and Yorkshire had both seen tactical voting to eject the Conservatives locally, spelling "bad news" for the governing party.

-With PTI Input