Labour will need to gain at least 106 seats in 2020 to secure a majority, after taking account of the forthcoming boundary changes, according to a thinktank analysis of the consequences of the party’s election defeat.

The Fabian Society concluded that Labour would require an electoral swing in marginal seats of 9.5 percentage points, more than twice the 4.6 points that the party needed for victory in 2015.

Labour’s leadership contenders are likely to examine the analysis closely, especially the emphasis on the need for the party to win over Tory voters, something Labour regarded as less important in the 2010-15 parliament due to the disillusionment with the Liberal Democrats.

The Fabians acknowledge that the chances of the next Labour leader securing an overall majority in 2020 look very small.



Andrew Harrop, the Fabian general secretary, says the finding shows the extent to which Labour faces a triple challenge in needing to “champion popular, big-tent politics to reach deep into middle England, revive support in Scotland and strengthen relationships with disillusioned voters in former heartlands”.

If Labour were to make no gains in Scotland, the party would need to perform better in England and Wales than at any time since the 1997 landslide.

The collapse of the Lib Dem vote means around four in five of the extra votes Labour will need to gain in English and Welsh marginals will have to come direct from Conservative voters. By comparison in 2015, this figure was about one in five.

The election has left Labour with 232 MPs, 94 short of a majority. To gain more than 47 seats, including one in Scotland, Labour needs swings of more than 5%. Even on swings of up to 7.5%, it regains only three seats in Scotland.



The Fabian analysis concludes that boundary changes mean Labour will have the equivalent of 220 MPs at the 2020 election, requiring it to win 106 seats. This compares with the 68 that Labour needed for a majority this year.

The 105th and 106th most marginal seats for Labour are now Harlow and Kirkcaldy, emphasising how Labour, to secure an overall majority, would need a broad-based approach that appeals to Scots and those on the edge of London.

The sobering figures for Labour on the size of the swing required implies its next leader will need to earn around 40% of the vote to win a majority of one, since it starts from a 2015 vote of 30.4%. If the party made no progress in Scotland, it would require a 42% vote share.

The Fabian analysis concludes that the situation is a remarkable reversal of electoral fortunes for Labour, which used to require fewer votes than the Conservatives did to win a majority. In 2005, Labour won a 66-seat majority with 35% of the vote, while it may well need 40% to have any majority at all.

By contrast, after the boundary changes, the Conservatives will be able to retain their majority with about 36% of the vote.

The results show the extent to which Scotland remains critical to Labour’s fortunes. It is possible Labour could recover faster in Scotland than elsewhere, considering the party is starting from such a low base with only one seat. If Labour could achieve a swing of around 11.5 points in its Scottish target seats, that would deliver 21 seats in Scotland, leaving 85 to be won in England and Wales.

The analysis suggests there is no option to try to win next time by squeezing the Lib Dem or Green vote, since together they won only 12% of the UK vote and slightly less in most of the marginal seats Labour now needs to win.