Rutherglen and Hamilton West by-election: Sir John Curtice says Labour could win 40 seats in Scotland if swing replicated at general election and compares victory to Tony Blair 1997 landslide

Labour candidate Michael Shanks has won the Rutherglen and Hamilton West by-election, with a swing of more than 20 per cent to seize the seat from the SNP

Labour’s overwhelming win in the Rutherglen and Hamilton West by-election could put the party on course for Downing Street if it is replicated across Scotland, polling expert Professor Sir John Curtice has said.

Labour candidate Michael Shanks won Scotland’s first recall by-election after securing more than twice the votes of his SNP rival Katy Loudon, in results Sir Keir Starmer hailed as “seismic”.

Sir John said that if Labour achieves the same higher-than-expected swing of more than 20 per cent across Scotland at the next general election, Sir Keir’s party could win 40 seats north of the border.

Labour Party leader Keir Starmer joined Scottish Labour leader Anas Sarwar (right) and MP-elect Michael Shanks (centre) to celebrate Shanks' victory in the Rutherglen and Hamilton West by-election. Picture: Jeff J Mitchell/Getty Images

The results confirm Labour poses “a serious challenge” to the SNP’s primacy at Westminster and has a momentum comparable with the run-up to the party’s 1997 landslide, according to the elections analyst.

Sir John said “with nearly 59 per cent of the vote, Labour’s share of the vote in the constituency is almost as high as it was back in the 2010 general election” before the party’s representation in Scotland collapsed.

“This is Labour apparently now able to put on the kind of performance that, frankly, it has not been able to put on at any stage since the independence referendum,” he said.

“And if – obviously it’s a big if – the swing since 2019 were to be replicated across Scotland as a whole, you are talking of Labour being back to having about 40 seats and the SNP being back down to not much more than half a dozen seats.”

He continued: “This result very firmly confirms the direction of travel indicated by the polls and that Labour do pose a serious challenge to the SNP’s continued dominance at Westminster.

“That potentially has implications for the overall outcome in the general election because if that were to happen, they would find it easier to get an overall majority.”

The increase in Labour’s vote in the seat to the south-east of Glasgow, as well as in the summer’s by-election in the North Yorkshire seat of Selby and Ainsty, “is the kind of results that you see in advance of general elections when parties are on course to win”, Sir John said.

“So, obviously, 12 months to go and all the rest of it, but I think one has to say that not only now are Labour clearly posing a serious, serious threat to the continuation of a deeply unpopular Conservative government south of the border, but they are now also posing a threat to a relatively unpopular – at least by its historical standards – SNP government north of the border.

“To that extent, I think they can reasonably claim to have done rather well.”

Sir John, professor of politics at Strathclyde University, said “these are the kind of swings you saw” before Sir Tony Blair swept to power in 1997.

He said the Tamworth by-election, triggered by the resignation of the former Tory whip Chris Pincher, which will be held on October 19, will “tell us much more than Rutherglen does about the probability of the party to win a general election”.