By Andrew MacAskill LONDON (Reuters) -British Prime Minister Keir Starmer's Labour Party won a surprise victory on Friday in a fiercely fought by-election for the Scottish parliament, while support for the right-wing Reform UK party surged in a contest tainted by a row over racism.

But there are "some caveats". Labour won a Westminster by-election there less than two years ago with a majority of about 9,500 and triumphed at the 2024 general election by a "similar margin", but this time they "squeaked through" on a "thin margin" margin of 602 votes.

Labour’s victory in a tight three-way Scottish by-election has opened up the race for next May’s Holyrood parliamentary elections, with Reform UK establishing itself as a serious contender.