Defeat in Blackpool South means the Conservatives have now lost 11 by-elections since the 2019 general election.

Four took place while Boris Johnson was prime minister while the remaining seven have all occurred during Rishi Sunak’s premiership.

It is the worst record for any government in a single parliament since the 1966-70 Labour administration of Harold Wilson, which clocked up 15 by-election losses.

Here is a full breakdown of the Tories’ by-election scorecard so far this parliament, which now stands at 11 defeats, one gain and three holds.

– Losses

1. Chesham & Amersham (June 17 2021)

The first defeat came in the Buckinghamshire constituency of Chesham & Amersham, in a by-election triggered by the death of the sitting Conservative MP Dame Cheryl Gillan.

The Liberal Democrats overturned Dame Cheryl’s 16,223 majority to win the seat on a huge swing of 25.2 percentage points, with party leader Sir Ed Davey celebrating by using a yellow hammer to demolish a “blue wall” of model bricks.

2. North Shropshire (December 16 2021)

Six months later, the Liberal Democrats took North Shropshire from the Conservatives on an even bigger swing of 34.1 points, overturning a majority of 22,949.

It remains the second largest by-election swing against any government since the Second World War, at contests where a seat had changed hands.

The by-election was triggered when the sitting Tory MP Owen Paterson resigned after he had been found to have breached House of Commons rules by engaging in paid lobbying.

Newly-elected Lib Dem MP Helen Morgan celebrated by using a long yellow pin to burst a large blue balloon.

3. Wakefield (June 23 2022)

The Conservatives suffered two by-election losses on the same day in June 2022: the first time since 1991 that a government had endured two concurrent defeats.

Labour took Wakefield in West Yorkshire on a swing of 12.7 percentage points and overturned a majority of 3,358 in what was the party’s first by-election gain from the Conservatives in 10 years.

The contest had been triggered by the resignation of sitting MP Imran Ahmad Khan, following a criminal conviction for child sexual assault.

4. Tiverton & Honiton (June 23 2022)

The other defeat came in the Devon seat of Tiverton & Honiton, where the Tories were defending a huge majority of 24,239 but which the Liberal Democrats won on another enormous swing, this time of 29.9 points.

The by-election was prompted by the resignation of sitting MP Neil Parish after he admitted watching pornography on his mobile phone in the House of Commons.

5. Selby & Ainsty (July 20 2023)

The Selby & Ainsty by-election in North Yorkshire was triggered by the resignation of sitting Tory MP Nigel Adams, who had a majority of 20,137, and saw Labour win the seat on a swing of 23.7 percentage points.

At 25 years old, winning candidate Keir Mather became the youngest MP in the House of Commons.

6. Somerton & Frome (July 20 2023)

On the same day that Labour gained Selby & Ainsty, the Liberal Democrats clocked up another win in the Somerset seat of Somerton & Frome, taking it from the Conservatives on a swing of 29.0 points and overturning a majority of 19,213.

The contest was triggered by the resignation of sitting MP David Warburton after an investigation into allegations of sexual harassment and cocaine use.

Sir Ed Davey celebrated his party’s by-election success by firing a cloud of yellow confetti from a blue circus cannon.

7. Mid Bedfordshire (October 19 2023)

In the first of another double-bill of same-day defeats, the Conservatives lost Mid Bedfordshire on a swing to Labour of 20.5 percentage points.

It remains the largest numerical Conservative majority (24,664) to be overturned by Labour at a by-election since 1945.

The contest had been triggered by the resignation of sitting MP Nadine Dorries.

8. Tamworth (October 19 2023)

Labour’s victory at Tamworth in Staffordshire saw a swing of 23.9 points: large enough to rank as the fourth biggest swing from Conservative to Labour at a by-election since 1945.

This was yet another contest prompted by the resignation of the sitting MP, in this case Chris Pincher, who won a majority of 19,634 in 2019 but who stood down after a Commons inquiry upheld allegations of sexual assault.

9. Kingswood (February 15 2024)

Labour overturned a majority of 11,220 to win this Gloucestershire seat, achieving a swing of 16.4 percentage points: lower than some of the huge swings it enjoyed in previous by-elections, but comfortably above the 11.4 percentage points it needed.

10. Wellingborough (February 15 2024)

In another instance of a same-day twin defeat for the Conservatives, Labour took the Northamptonshire seat of Wellingborough on an enormous swing of 28.5 percentage points: the second biggest swing from Tory to Labour at a by-election since the Second World War.

The Conservatives’ share of the vote slumped from 62% at the 2019 general election to just 25%, the largest drop recorded by the Tories at any by-election since 1945.

11. Blackpool South (May 2 2024)

The latest by-election defeat for the Conservatives saw Chris Webb gain Blackpool South for Labour on another mammoth swing, this time of 26.3 percentage points: the third largest swing of its kind at a by-election since the war.

The result saw the Tories almost pushed into third place by the Reform Party, which won 17% of the vote – its best-ever performance in a by-election.

– Gains

Hartlepool (May 6 2021)

The Conservatives have made one by-election gain during this parliament: Hartlepool in County Durham, which the party took from Labour on a swing of 16.0 percentage points.

Labour had held the seat since it was created in 1974.

Prime Minister Boris Johnson hailed the result as support for his Government’s “levelling up agenda”, which also came in the wake of the successful roll-out of the first Covid-19 vaccinations.

– Holds

1. Old Bexley & Sidcup (December 2 2021)

The Conservatives held this London seat in a by-election triggered by the death of MP James Brokenshire.

2. Southend West (February 3 2022)

The Tories held this Essex seat in a contest triggered by the murder of MP David Amess.

3. Uxbridge & South Ruislip (July 20 2023)

This by-election for a seat in outer London took place on the same day as the Conservatives lost Selby & Ainsty to Labour and Somerton & Frome to the Lib Dems.

In this instance, the party held the seat, in a contest triggered by the resignation of its MP and former prime minister Boris Johnson.

Labour needed a swing of 7.6 points to win, far smaller than the swing the party achieved in Selby & Ainsty, but managed only 6.7 points.

Both parties suggested the expansion of London’s ultra-low emission zone (Ulez), which levies a charge on vehicles that do not meet certain emissions standards and is a key policy of Labour mayor Sadiq Khan, may have contributed to the result.