• Labour looking to retain new mayor's seat in test for Corbyn
  • Tories increased vote share in Tooting district last year

A House of Commons by-election to choose a lawmaker to succeed new London Mayor Sadiq Khan will be held on June 16, one week before the U.K. votes on whether to leave the European Union.

The election, in south London’s Tooting district, will be a test of support for both the ruling Conservative and opposition Labour parties. Khan won the seat for Labour in last year’s general election with a 47 percent share of the vote, but the Conservative candidate won 42 percent in an improvement on the Tories’ 2010 performance.

Wandsworth Borough Council confirmed the date for the vote by phone Wednesday. It will mean Tooting’s voters have to go to the polls three times in seven weeks, following last week’s mayoral contest.

The contest will be the first parliamentary by-election in southern England for Labour since Jeremy Corbyn became leader in September. While Khan gained a record vote in the mayoral contest, he distanced himself from Corbyn’s hard-line socialist policies during the campaign.

Labour lost ground in other elections around the U.K. last week, particularly in Scotland. Corbyn told lawmakers on Monday that the party will need to perform better or it is on course to lose the 2020 general election.

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