North-west England is home to some of the tiniest parliamentary majorities in the country and is a region where even a small shift of opinion by voters could have big consequences on polling day.

A redrawing of boundaries has given the North West 73 constituencies, down from 75 in 2019, and had the last election been fought on these new boundaries it is calculated Labour would have won 41 seats and the Conservatives 31, with the Speaker – Sir Lindsay Hoyle – holding his seat of Chorley.

Notional results for the 2019 election based on the 2024 boundaries have also been calculated, in order to determine the scale of the challenge facing candidates this time, and it is these majorities that are used below.

A good measure of the critical role the North West will play in determining the outcome of the election is the number of marginal seats in the region.

There are six constituencies with majorities under 1,000, while 21 have majorities below 5,000.

Of the six with a majority under 1,000, three are being defended by Labour: Warrington South (whose redrawn boundaries mean it is being treated as a Labour defence), Wirral West and Heywood & Middleton North; and three are being defended by the Conservatives: Burnley, Leigh & Atherton and Bury South.

Burnley is not merely Labour’s top target in the North West; it is also the party’s top target in the whole of mainland Britain, due to the tiny 0.2-percentage point swing needed to take the seat from the Tories.

A total of 10 seats would change hands on a swing from the Conservatives to Labour of just 4.4 percentage points, including both Bury South and Bury North, Bolton North East, Lancaster & Wyre, Hyndburn and Blackpool South.

If Labour manages to push the swing up to 10 percentage points, 17 Tory seats would fall to the party, including South Ribble, Rossendale & Darwen and Macclesfield.

South Ribble is an example of a so-called “bellwether”, which means the result in the constituency has a habit of matching the overall result of the general election – in this instance, at every election since the seat was created in 1983.

Macclesfield has been held by the Conservatives continuously since 1918 and a Labour win here would be a historic first.

An exceptional performance by Sir Keir Starmer’s party in the North West might even see the seat of Tatton change hands.

This is a seat that was once represented by former chancellor George Osborne and whose most recent Tory MP was the Government minister Esther McVey.

Ms McVey is a candidate at this election and is defending a majority of 19,281, with Labour needing a huge swing of 17.4 percentage points to defeat her.

In Rochdale, leader of the Workers’ Party George Galloway will be hoping to hold the seat he won from Labour at a by-election in February this year.

The Workers’ Party have a total of candidates in 152 constituencies across the country.

There has been such a drastic redrawing of the boundaries of Westmorland & Lonsdale, won in its old guise by Tim Farron for the Liberal Democrats at every election since 2005, that it is now being treated as a seat that would have returned a Tory MP in 2019.

As such it is one of the Lib Dems’ top targets in the region, in which Mr Farron is once again a candidate.

The party’s two other targets in the North West are Cheadle, which the Lib Dems held from 2001 to 2015, and Hazel Grove (Lib Dem from 1997 to 2015).

All three would change hands on a direct swing from the Tories to the Lib Dems of 4.8 percentage points and are further examples of seats in the North West that could switch allegiance on polling day thanks to only a modest shift in public opinion.

All notional majorities and swings mentioned above have been compiled by professors Colin Rallings and Michael Thrasher of the University of Plymouth, on behalf of BBC News, ITV News, Sky News and the PA news agency, and will be used as the basis for reporting the gains and losses at the General Election.