“It was the UKIP vote that disproportionately hurt the Labour party in the 2015 General Election, and there wouldn’t have been a Conservative majority if it hadn’t been for the effect of the UKIP vote”

That was Nigel Farage’s claim today as he kicked off the Brexit Party’s election campaign.

He’s trying to court the Conservatives with the offer of a “Leave alliance.” If the Prime Minister doesn’t agree, Mr Farage says his party will field candidates in “every single seat” in England, Scotland and Wales.

He’s harking back to 2015 — the last time the Conservatives won an overall majority in Parliament — to make his case.

But the available evidence suggests Mr Farage is wrong about the role of his former party, UKIP, in that election.

What happened in 2015?

Mr Farage’s claim seems to be that Labour lost more voters to UKIP in 2015 than the Conservatives did.

Dr Jonathan Mellon from the British Election Study (BES) — widely considered to be the gold-standard of UK voting analysis — told FactCheck that in his view, “this statement is incorrect.”

He pointed us to research he and Oxford University Professor Geoffrey Evans conducted in early 2015, which found that “UKIP drew most of its support from 2010 Conservatives rather than Labour.” In other words, the Conservatives might have done even better in that election were it not for UKIP.

He tells FactCheck “it’s certainly not the case that UKIP disproportionately attracted Labour voters in 2015.”

And there’s further evidence that Mr Farage’s former party was a greater threat to the Conservatives than Labour in 2015. BES data reveals that more than 40 per cent of those who planned to vote UKIP in 2015 would chose the Conservatives as their second choice. That’s more than twice the number of UKIP voters who would otherwise opt for Labour.

It’s worth saying that this research is based on data up to 2014, but Dr Mellon points out that “the story is much the same if we look at actual vote choice in [the] 2015 [election].” And as it was conducted by the BES, it’s the closest we can get to the final word on the matter.

And it’s further endorsed by BES evidence from 2017, which shows that the Conservatives took far more ex-UKIP voters than Labour did. This bolsters the theory that people who voted UKIP in 2015 saw their choice as one of Conservatives vs UKIP rather than Labour vs UKIP.

What’s less clear is exactly how significant the 2015 effect was in individual constituencies. In their book, The British General Election 2015, Professors Philip Cowley and Dennis Kavanaugh say that “the Conservatives certainly lost more support where UKIP did best.” Though they point out that “the same also happened to Labour.” Nevertheless, they agree that the extent of this was slightly worse for the Conservatives, albeit “marginally.”

Since we published this article, the Brexit Party contacted us to share three articles relating to Mr Farage’s claim. One quoted a UKIP candidate saying that “the reason the Tories have won the key battleground of the Midlands is that UKIP came to their rescue.” The other two focused on how UKIP may have hindered Labour’s chances in some seats. Neither quote British Election Study data.

FactCheck verdict

Nigel Farage said that votes for UKIP, the party he was leading at the time, “disproportionately hurt the Labour party in the 2015 General Election,” and that “there wouldn’t have been a Conservative majority if it hadn’t been for the effect of the UKIP vote.”

The implication is that the Brexit Party he now leads will split Labour’s vote rather than the Conservatives’ in the upcoming election. It’s part of Mr Farage’s offer of a “Leave alliance” with the Conservatives.

But his account of the 2015 result is contradicted by the available evidence, which suggests the Conservatives won a majority despite UKIP, not because of it, and were affected more negatively than Labour.

The Brexit Party have been approached for comment.